If you go to Yoda's Help Desk at http://www.lucasarts.com
you can look up patches for games.
JK has the 1.01 patch, and you might as well install it, but it may not make a difference.
Is JK the only 3d game you have problems with? You might simply need to reinstall the game (might work).
Some other things you could try, would be to make sure you are using a stable and recent version of DirectX (I used 5.0, 6.1, 7.0a and 8.0 with JK and never had problems). You could also install the latest drivers for your video card and see if that helps.
You can also check out the help files and troubleshooting for JK at Yoda's Help Desk.