I had the same problem, had the SDK beta installed and followed the directions and it worked the first time. Let me summarize what I got from about three posts and put it in one place:
(1) Reboot after a lock-up then exit from Steam
(2) Copy your "user.ini" and "RedOrchestra.ini" files from C://(whatever)/Steam/SteamApps/(username)/RedOrchestra/system; don't leave them in that directory. I copied them to a file in My Documents that I named "RO Backups".
(3) Go back to the RO directory in SteamApps and delete everything in the RO directory, but by "select all" then "delete", don't delete the directory.
(4) Re-boot your computer again.
(5) Check your shortcut on your desktop to be sure there's no extra wording in the shortcut's Properties.
(6) Start the game using your desktop shortcut. You will see that the display is wrong, but that's okay. Try to join a server. If you succeed, exit RO and then go on.
(7) Copy your "RedOrchestra.ini" and "user.ini" files back into the system folder in the RO game folder. You will find those folders there, even though you just deleted all from the "RO" folder.
(8) Start RO again using the shortcut. It should be back to what it was, maybe even a bit better.
Worked fine for me. But I do hope they get that bug fixed in the SDK or whatever it is, because I'd really like to mod RO:O. I was even learning how to do that! Imagine! You see: you can teach an old dog new tricks; it just takes a long time!