Ask your friend if he installed MTA:VC.
This bug is a real popular one among users of MTA:VC. The reason being for the unhandled exception is that MTA:VC is attempting to modify the game code to support multiplayer but do realize that something can go wrong.
MTA:VC 0.2 is in the works and should iron out many bugs, including this one.
If it's not this, then I'm stumped.
Edit: Website of MTA:VC is
www.multitheftauto.com