I had the exact same problem (UT2003.exe has encountered a problem and needs to close. We are sorry for the inconvenience.) the same exact message .
So I used an anti-virus program on the machine and it found a virus that attackes setup.exe files win.ipini something like that . Anyhow after running the virus software the game runs fine. Also many others run well too ..the problem crept up into lots of things.
Anyhow give it a shot perhaps it will work for you too.