It may be that your problem is only with the override heads (overrides are only neccessary so you can see the heads at character creation because it doesnt load the haks untill it loads the module when you log onto the server.)
If the problem is only with the override files and not a problem with your card/settings having trouble with the textures, then the only place they will look wrong is at character creation.
Basically, they may look fine IG since it displays them from the haks. Acctually, you may have to take out the override heads to get it to display from the haks.
But it will still be difficult to choose a head and hair color if you're not seeing the textures so... ideally redownloading and/or updating your video card drivers will fix it.
-TV
Edit: *points up* aha! I knew my theory was good. Try just picking one that you think is the one you want and then go IG and see if it works. You can always have the character deleted and try again if it ends up being one you dont want. But still try redownloading and updating your video drivers. Perhaps that will solve the problem all together.