You might have to uninstall then reinstall the game. I'm running SP2 and have no problems with it and BF2.
The game is really buggy and you can get conflicts with just about any program, but like I said, sometimes you just have to re-install.
I don't even bother troubleshooting anymore because it doesn't do any good.
You can save your profile, it's in your documents folder.
I forgot to add, anything you want to know about BF2 tweaking can be found here:
TweakGuides.com - Battlefield 2 Tweak Guide