swapped Radeon -> NVidia - just delete Radeon libdrm_radeon1 ?

I tried just swapping the cards (ATI Radeon HD6450 -> EVGA 8400GS), assuming OS 12.3 Neuveau would figure out it needed to change something, but it didn't - I get the startup splash screen, but not the KDE boot screen, etc., and not a desktop. So I have to boot into Recovery Mode. I've been looking through the threads but don't see this addressed.

Thanks,
Patti