I haven't been able to start an MP game on the v2.3 opt-in branch for several days now. I've tried verifying integrity via Steam and even reinstalling the game (and deleting anything left over in Documents) to no avail.
Anyway, I've been sending in the crash reports, but the game barfs on the building galaxy (first step) stage when trying to start a MP game. SP seems to work fine.
Any idea what might be going on? I know GC3 is primarily focused on SP, but the multiplayer issues are really starting to take the wind out of my sails for this game. I was looking forward getting some fixes in 2.3 for things like Ideology events not firing and initial client crash in MP (which you could work around by having the host save on turn 1 and then restoring that session), but now I can't even play the game at all.