I have the same problem, I would love if someone could help me.
I have windows XP, I just downloaded UP 3.0 RC4, I have the UP 3.0 RC4 Splash screen on loading, but a few seconds after it gets to the "home" menu of IL-2, it just crashes to the desktop. If I very rapidly click QMB, then just press fly, it loads completely, but then crashes right when the in-game flight should begin.
I can post my Logfile if it would help.
Thanks for any help!