Unfortunately you can't uninstall DirectX... I have only gone to DirectX 7 on my PC since I don't use it a lot anymore and it's "ancient"... but I remember that lovely piece of software well, I always crossed everything I could before installing!
It usually goes well but now and then, not. Have you tried running all the tests that come with it? I can access them by running dxdiag.exe and working through the tabs, if v9 is still the same sort of thing. Also see if any of the drivers are marked with exclamations or "x's" so forth to indicate if there is a problem.
You don't mention what OS you are running but if it's ME or XP... is there any chance you can do a system restore?
There's more info here:
Direct X 9If you don't have any luck with any of this and no one else has any ideas there's a great Windows support board listed in our "links" sections accessible at the bottom of the page.
Chances are good someone there may have run into something similar...
