full crash log here: http://paste.fedoraproject.org/214968/25397142

after downgrading to try to deal with a problem I was having with the new version, I ended up with THIS problem:
[17:35:53] [Server thread/ERROR] [FML]: A dependency cycle was detected in the input mod set so an ordering cannot be determined
[17:35:53] [Server thread/ERROR] [FML]: The first mod in the cycle is FMLMod:CoFHCore{1.7.10R3.0.2}
[17:35:53] [Server thread/ERROR] [FML]: The mod cycle involves
[17:35:53] [Server thread/ERROR] [FML]: FMLMod:CoFHCore{1.7.10R3.0.2} : before: [], after: [FML@[7.10.0.1291,7.11), Forge@[10.13.1.1291,10.14)]
[17:35:53] [Server thread/ERROR] [FML]: APIContainer{CoFHLib:1.7.10R1.0.0B9} : before: [EnderTech], after: [CoFHCore]
[17:35:53] [Server thread/ERROR] [FML]: FMLMod:AncientWarfare{2.4.83-beta-MC1.7.10} : before: [], after: [BuildCraft|Core, CoFHCore]
[17:35:53] [Server thread/ERROR] [FML]: APIContainer{CoFHAPI|energy:1.0} : before: [redgear_core, ExtraUtilities, funkylocomotion, BuildCraft|Silicon, BuildCraft|Core, BuildCraft|Transport, BuildCraft|Builders, BuildCraft|Energy, BuildCraft|Factory, minechem, CoFHCore, Forestry, Railcraft, EnderTech, EnderIO, simplyjetpacks, CartLivery, BloodArsenal], after: [CoFHCore]
[17:35:53] [Server thread/ERROR] [FML]: Dummy Container (After) @2091383113 : before: [], after: []
[17:35:53] [Server thread/ERROR] [FML]: APIContainer{CoFHAPI:1.7.10R1.0.7} : before: [EnderTech, Railcraft, BuildCraft|Silicon, BuildCraft|Core, BuildCraft|Transport, BuildCraft|Builders, BuildCraft|Energy, BuildCraft|Factory, Forestry, funkylocomotion, EnderIO, redgear_core, minechem, ExtraUtilities, BuildCraft|Compat, simplyjetpacks], after: [CoFHLib]
[17:35:53] [Server thread/ERROR] [FML]: Dummy Container (AfterAll) @1683088548 : before: [], after: []
[17:35:53] [Server thread/ERROR] [FML]: FMLMod:AncientWarfareAutomation{2.4.83-beta-MC1.7.10} : before: [], after: [AncientWarfare]
[17:35:53] [Server thread/ERROR] [FML]: FMLMod:BuildCraft|Core{6.4.13} : before: [], after: [Forge@[10.13.2.1236,)]

likely one of the mod updates I attempted created this cycle, but I have no idea whats wrong. The new version tries to run, but creates a worldgen error, and this one's ordering is all wrong.

all the files in mods directory:
http://pastebin.com/K5sAEuTM

it is quite surprising how many mods include the api files in their jars XD

cofh really ought to write something into their mod to force a crash when mods do this

AFAIK, this is related to CoFH api, and maybe Buildcraft.
Make sure you only have one instance of the API, by searching inside each mod jar a top directory called "cofh", and remove it. Only leave the one in CoFHCore.
The official AncientWarfare does not contain the CoFH api.

pulling ancientwarefare eliminated the problem though.
I don't WANT to remove it permanently. Its just odd. I'll try what you said.

I would look at EnderIO and EnderTech first. Then ExtraUtilities and Forestry.

It seems to happen only sometimes during server/client launch. Absolutely no idea why this wouldn't be deterministic. Perhaps there is an element of randomness in the sorting algorithm?

When there are duplicate classes like you seem to have, the loading order is not deterministic. Depends on ram state, basically.
Just follow my advice. This is not an issue that AW can solve. (except by removing any RF support, to let someone else handle the mismatching crash report)