So, just another update. I still have the problem, but I have some more hope for those experiencing a similar issue.
A friend of mine was also familiar with this issue and I advised him I could not join friends' games because of it. I had to host. He told me try joining a game from the main menu after plugging the Retaliation back in and I should be able to accept a request to join a game. It worked!
However, I locked up the first time I tried to do it because I went to the main menu from multiplayer and that probably made it check my DLC again and connect again. I had to restart my Xbox before attempting it. I should have just dashboarded. I would have had to take out the DLC again before loading up but it would have prevented the freeze.
Either way if anyone is searching for help on this matter this is what I have so far. It's unfortunate that Bioware isn't devoting any time to this game any more.
I am having this same problem on 360, and the only workaround I've found so far is to delete and re-download retaliation each time I want to play. EA support was not helpful.
See above where I point out a slight workaround to this. Install retaliation on a USB drive. Plug it in after it checks for DLC at the main menu. You can accept invites to friends' games at this point also. You cannot if you go into multiplayer as it will take you back to the main menu momentarily to check and it will freeze as if you came to the menu with Retaliation installed. If you go into multiplayer you will have to host or quick join a random game.
