Breaking the powering wire directly attached to the lamp block it powers crashes the server. Doing something similar with the PR Comparator crashes the server as well. Singleplayer reproducibility has not been tested.

Cant help without a log.

[21:26:46] [Server thread/INFO]: Preparing level "world"
[21:26:48] [Server thread/INFO]: Preparing start region for level 0
[21:26:49] [Server thread/INFO]: Preparing spawn area: 48%
[21:26:50] [Server thread/INFO]: Preparing spawn area: 87%
[21:26:50] [Server thread/INFO]: Done (3.777s)! For help, type "help" or "?"
[21:26:52] [Server thread/WARN]: Can't keep up! Did the system time change, or is the server overloaded? Running 2123ms behind, skipping 42 tick(s)
[22:56:32] [User Authenticator #1/INFO]: UUID of player DeathChain01 is 44c256a9173a4df0a3117aa7cd8c8818
[22:56:33] [Server thread/INFO]: DeathChain01[/96.233.144.233:64113] logged in with entity id 303 at (143.85696579336252, 68.75888139404296, 115.12654220596418)
[22:56:33] [Server thread/INFO]: DeathChain01 joined the game
[22:58:25] [Server thread/WARN]: Failed to handle packet for /96.233.144.233:64113
net.minecraft.util.ReportedException: Exception while updating neighbours
at net.minecraft.world.World.func_147460_e(World.java:707) ~[afn.class:?]
at mrtjp.projectred.core.TAcquisitionsCommons$class.notifyStraight(connparts.scala:19) ~[TAcquisitionsCommons$class.class:?]
at mrtjp.projectred.transmission.WirePart.notifyStraight(wireabstracts.scala:203) ~[WirePart.class:?]
at mrtjp.projectred.core.TFaceConnectable$$anonfun$notifyAllExternals$1.apply$mcVI$sp(connparts.scala:360) ~[TFaceConnectable$$anonfun$notifyAllExternals$1.class:?]
at scala.collection.immutable.Range.foreach$mVc$sp(Range.scala:141) ~[Range.class:?]
at mrtjp.projectred.core.TFaceConnectable$class.notifyAllExternals(connparts.scala:358) ~[TFaceConnectable$class.class:?]
at mrtjp.projectred.transmission.WirePart.notifyAllExternals(wireabstracts.scala:203) ~[WirePart.class:?]
at mrtjp.projectred.transmission.TWireCommons$class.onRemoved(wireabstracts.scala:76) ~[TWireCommons$class.class:?]
at mrtjp.projectred.transmission.RedAlloyWirePart.onRemoved(redwires.scala:305) ~[RedAlloyWirePart.class:?]
at codechicken.multipart.TileMultipart.remPart_do(TileMultipart.scala:359) ~[TileMultipart.class:?]
at codechicken.multipart.TileMultipart.remPart_impl(TileMultipart.scala:332) ~[TileMultipart.class:?]
at codechicken.multipart.TileMultipart.remPart(TileMultipart.scala:327) ~[TileMultipart.class:?]
at codechicken.multipart.TMultiPart.harvest(TMultiPart.scala:110) ~[TMultiPart.class:?]
at codechicken.multipart.TileMultipart.harvestPart(TileMultipart.scala:444) ~[TileMultipart.class:?]
at codechicken.multipart.BlockMultipart.removedByPlayer(BlockMultipart.scala:117) ~[BlockMultipart.class:?]
at net.minecraft.server.management.ItemInWorldManager.func_73079_d(ItemInWorldManager.java:243) ~[mn.class:?]
at net.minecraft.server.management.ItemInWorldManager.func_73084_b(ItemInWorldManager.java:274) ~[mn.class:?]
at net.minecraft.server.management.ItemInWorldManager.func_73074_a(ItemInWorldManager.java:151) ~[mn.class:?]
at net.minecraft.network.NetHandlerPlayServer.func_147345_a(NetHandlerPlayServer.java:486) ~[mx.class:?]
at net.minecraft.network.play.client.C07PacketPlayerDigging.func_148833_a(SourceFile:53) ~[iw.class:?]
at net.minecraft.network.play.client.C07PacketPlayerDigging.func_148833_a(SourceFile:8) ~[iw.class:?]
at net.minecraft.network.NetworkManager.func_74428_b(NetworkManager.java:197) ~[ef.class:?]
at net.minecraft.network.NetworkSystem.func_151269_c(NetworkSystem.java:165) [ms.class:?]
at net.minecraft.server.MinecraftServer.func_71190_q(MinecraftServer.java:643) [MinecraftServer.class:?]
at net.minecraft.server.dedicated.DedicatedServer.func_71190_q(DedicatedServer.java:326) [lj.class:?]
at net.minecraft.server.MinecraftServer.func_71217_p(MinecraftServer.java:531) [MinecraftServer.class:?]
at net.minecraft.server.MinecraftServer.run(MinecraftServer.java:414) [MinecraftServer.class:?]
at net.minecraft.server.MinecraftServer$2.run(MinecraftServer.java:669) [kx.class:?]
Caused by: java.lang.UnsupportedOperationException: empty.max
at scala.collection.TraversableOnce$class.max(TraversableOnce.scala:216) ~[TraversableOnce$class.class:?]
at scala.collection.SeqViewLike$AbstractTransformed.max(SeqViewLike.scala:43) ~[SeqViewLike$AbstractTransformed.class:?]
at codechicken.multipart.TileMultipart.getLightValue(TileMultipart.scala:178) ~[TileMultipart.class:?]
at codechicken.multipart.BlockMultipart.getLightValue(BlockMultipart.scala:222) ~[BlockMultipart.class:?]
at net.minecraft.world.World.func_98179_a(World.java:2927) ~[afn.class:?]
at net.minecraft.world.World.func_147463_c(World.java:3057) ~[afn.class:?]
at mrtjp.projectred.illumination.BaseLightPart.updateRender(lightpart.scala:109) ~[BaseLightPart.class:?]
at mrtjp.projectred.illumination.BaseLightPart.updateState(lightpart.scala:100) ~[BaseLightPart.class:?]
at mrtjp.projectred.illumination.BaseLightPart.onNeighborChanged(lightpart.scala:67) ~[BaseLightPart.class:?]
at codechicken.multipart.TileMultipart$$anonfun$onNeighborBlockChange$1.apply(TileMultipart.scala:165) ~[TileMultipart$$anonfun$onNeighborBlockChange$1.class:?]
at codechicken.multipart.TileMultipart$$anonfun$onNeighborBlockChange$1.apply(TileMultipart.scala:165) ~[TileMultipart$$anonfun$onNeighborBlockChange$1.class:?]
at codechicken.multipart.TileMultipart.operate(TileMultipart.scala:75) ~[TileMultipart.class:?]
at codechicken.multipart.TileMultipart.onNeighborBlockChange(TileMultipart.scala:165) ~[TileMultipart.class:?]
at codechicken.multipart.BlockMultipart.func_149695_a(BlockMultipart.scala:85) ~[BlockMultipart.class:?]
at net.minecraft.world.World.func_147460_e(World.java:674) ~[afn.class:?]
at mrtjp.projectred.transmission.PropagationRun$$anonfun$finish$2.apply(propagation.scala:132) ~[PropagationRun$$anonfun$finish$2.class:?]
at mrtjp.projectred.transmission.PropagationRun$$anonfun$finish$2.apply(propagation.scala:132) ~[PropagationRun$$anonfun$finish$2.class:?]
at scala.collection.Iterator$class.foreach(Iterator.scala:727) ~[Iterator$class.class:?]
at scala.collection.AbstractIterator.foreach(Iterator.scala:1157) ~[AbstractIterator.class:?]
at scala.collection.IterableLike$class.foreach(IterableLike.scala:72) ~[IterableLike$class.class:?]
at scala.collection.AbstractIterable.foreach(Iterable.scala:54) ~[AbstractIterable.class:?]
at scala.collection.immutable.HashSet$HashSetCollision1.foreach(HashSet.scala:180) ~[HashSet$HashSetCollision1.class:?]
at scala.collection.immutable.HashSet$HashTrieSet.foreach(HashSet.scala:306) ~[HashSet$HashTrieSet.class:?]
at mrtjp.projectred.transmission.PropagationRun.finish(propagation.scala:132) ~[PropagationRun.class:?]
at mrtjp.projectred.transmission.PropagationRun.runLoop(propagation.scala:164) ~[PropagationRun.class:?]
at mrtjp.projectred.transmission.PropagationRun.start(propagation.scala:146) ~[PropagationRun.class:?]
at mrtjp.projectred.transmission.WirePropagator$.propagateTo(propagation.scala:71) ~[WirePropagator$.class:?]
at mrtjp.projectred.transmission.WirePropagator$.propagateTo(propagation.scala:77) ~[WirePropagator$.class:?]
at mrtjp.projectred.transmission.TWireCommons$class.onNeighborChanged(wireabstracts.scala:54) ~[TWireCommons$class.class:?]
at mrtjp.projectred.transmission.WirePart.onNeighborChanged(wireabstracts.scala:203) ~[WirePart.class:?]
at codechicken.multipart.TileMultipart$$anonfun$onNeighborBlockChange$1.apply(TileMultipart.scala:165) ~[TileMultipart$$anonfun$onNeighborBlockChange$1.class:?]
at codechicken.multipart.TileMultipart$$anonfun$onNeighborBlockChange$1.apply(TileMultipart.scala:165) ~[TileMultipart$$anonfun$onNeighborBlockChange$1.class:?]
at codechicken.multipart.TileMultipart.operate(TileMultipart.scala:75) ~[TileMultipart.class:?]
at codechicken.multipart.TileMultipart.onNeighborBlockChange(TileMultipart.scala:165) ~[TileMultipart.class:?]
at codechicken.multipart.BlockMultipart.func_149695_a(BlockMultipart.scala:85) ~[BlockMultipart.class:?]
at net.minecraft.world.World.func_147460_e(World.java:674) ~[afn.class:?]
... 27 more
[22:58:25] [Server thread/INFO]: DeathChain01 lost connection: TextComponent{text='Internal server error', siblings=[], style=Style{hasParent=false, color=null, bold=null, italic=null, underlined=null, obfuscated=null, clickEvent=null, hoverEvent=null}}
[22:58:25] [Server thread/INFO]: DeathChain01 left the game
[22:59:13] [Server thread/INFO]: Stopping the server
[22:59:13] [Server thread/INFO]: Stopping server
[22:59:13] [Server thread/INFO]: Saving players
[22:59:13] [Server thread/INFO]: Saving worlds
[22:59:13] [Server thread/INFO]: Saving chunks for level 'world'/Overworld
[22:59:14] [Server thread/INFO]: Saving chunks for level 'world'/Nether
[22:59:14] [Server thread/INFO]: Saving chunks for level 'world'/The End

You are using an older version of FMP, as this was fixed in the one of the newer ones.