STEP 1 : Download http://users.edpnet.be/zepilot/debug.faf
STEP 2 : put it in : c:\ProgramData\FAForever\gamedata\
STEP 3 : Make sure LOGS are enabled (options - settings - save game logs)
STEP 4 : Make a test lobby.
STEP 5 : wait that it crash.
STEP 6 : Pastebin the log (game.log, not faforever.log) immediatly before doing anything else.
STEP 7 : remove the debug.faf if you want to play or it will make your game lag as hell.
You can read the pastebin and make your wild guess.