I recently decided to upgrade to the latest OmegaDrivers(.net), after doing so CoD1 and HL1 based games wouldnt work (menu buttons had a 2sec response time). I then reverted back to my older drivers which worked fine but then discovered the problem was still not gone. I now cant play CoD1 or any HL1 based games but HL2 based games and UT2004 works.
I think the nature of this problem is concerned with the windows registry. Basically when you updated the drivers for the game the registry got changed and so the system tries to adjust the games (programs settings) accordingly. But this is an automated programmed task and sometimes these things dont always go so smoothly as they should.
OK! to undo the registry changes you would have too now uninstall the whole game and the drivers (new & old one too). Using control panel (assuming your running windows of course?) add & remove programs. Yes! once un-installed you must be careful and definately re-boot the machine BEFORE!! you then re-install the entire game (program) & drivers too. (NOTE: If you dont reboot the system the windows registry wont be updated on removal & a second reboot would be required after the program is re-installed again to update the registry settings.
After that both game & drivers should works fine as before. Its a long winded way of repairing the whole thing.