I went to install a new mod once. Clicked on the Mod Manager out of the launcher. It took awhile to "Scan for rF2 mod files" and then it came up with a message box that said "Out of memory" then the mod manager opened... but without any mods. Upon clicking refresh, the same thing happened, except the Scanning for rF2 mod files took much shorter (less than a second versus 10+ seconds). Confused I went back to the launcher, clicked on single player, and then got a run time error. Same thing when I clicked on Multiplayer. Mod dev mode worked perfectly fine, however. (Actually used the time to figure out how to put a Porsche 917 engine in the Skip Barber car ) I'm on Windows XP. I tried uninstalling, reinstalling, clearing out my packages folder, etc. Nothing worked.
have you multiple wheel/joypad ?? If yes, have you disconnect one of them?? Try to re-connect all the peripherals...