Running Mekanism v6.0.5.46
Running Forge Server v9.11.1.965
Minecraft v1.6.4
I experienced no issues using client only and I JUST started my own server last night. I put in the Digital Miner today and had no issues till logging out, server still running. Immediately after logging out the server had a fatal crash and won't come back up. No loss, I'm the only one on it and it's only been up for 18 hours. Let me know if you need the full report and thank you for the awesome mod and all your hard work :-))))

---- Minecraft Crash Report ----
// On the bright side, I bought you a teddy bear!

Time: 8/14/14 3:58 PM
Description: Ticking tile entity

java.lang.NullPointerException
at mekanism.api.Coord4D.get(Coord4D.java:176)
at mekanism.common.util.TransporterUtils.insert(TransporterUtils.java:152)
at mekanism.common.tile.TileEntityDigitalMiner.onUpdate(TileEntityDigitalMiner.java:243)
at mekanism.common.tile.TileEntityBasicBlock.func_70316_g(TileEntityBasicBlock.java:54)
at net.minecraft.world.World.func_72939_s(World.java:2209)
at net.minecraft.world.WorldServer.func_72939_s(WorldServer.java:550)
at net.minecraft.server.MinecraftServer.func_71190_q(MinecraftServer.java:668)
at net.minecraft.server.dedicated.DedicatedServer.func_71190_q(DedicatedServer.java:276)
at net.minecraft.server.MinecraftServer.func_71217_p(MinecraftServer.java:587)
at net.minecraft.server.MinecraftServer.run(MinecraftServer.java:484)
at net.minecraft.server.ThreadMinecraftServer.run(SourceFile:583)

Looks like this may be a known issue, sorry if it is redundant but I hope the extra info helps :-)

Yes, this is fixed in v7 :)