I'm having this same issue, but unlike the people above, I can't get it fixed at all.
I tried force updating, downloading a new launcher, downloading the linked xlive.dll, but nothing changes (well, except for the delay in joining the servers and the error message; before I downloaded the new launcher it was instant, now it takes like 3 seconds). The launcher window says it's version 2.3.1.0, in-game text says it's v0.3.1.0 and it also says I'm connected to the master server. I also tried deleting my xlive.dll file, but neither the launcher nor the game itself downloads a new one, in fact, the game tries to connect me to the original Windows Live or whatever.
My connection is fine, as I can play any other game online without any issues :/