According to Chief, XP apps won't run on Vista. How old is your monitor? Tell us your specs and as much as possible.
Also, have you tried playing JOE on DX9? DX10 was designed to make the most out of the ''today's games'', not 2004ish games. (Or how old JOE is.)
And play JOTR itself without JOE just to see if it's the game or your PC. I'd also play other games to see if this happens too.
Good luck.
Chris
