Hmmm. There are a few things that could crash multiplayer.
Are you trying to play an IP game? I can't remember if TBP was supported by FS2NetD or not (If it isn't it would give you messages about hacked tables but should still work - are you seeing those before the crash?)
If you're trying to play on FS2NetD have you registered and entered your details into the multiplayer options screen?
Either way take a look at my FAQs gameplay section as the multiplayer help in there (even though it goes on about FS2) may help you. Don't use the old edition build though as that won't work with TBP
