I run a limited account as my main account on an WinXP box. I installed Vendetta as the admin account, and now when I try to run the game as my limited account, it crashes ("vendetta.rlb has encountered an error and needs to close" or something similar to that). If I run it as the admin, it's fine.
I'm guessing that this may be a file permissions error (because that's what it's been when I've run into admin/limited issues with games before)
Let me know if you need any more information.