Patched Kernel causes incompatibilities?

I am running 8.1 on an AMD Athlon, VIA KT400 chipset. I have noticed that when I use YOU to upgrade to the latest kernel for amd processors, one of my NICs stops working, and the nvidia 3D driver crashes the computer. Using rpm to downgrade back to the kernel on the CD, everything works fine again. I have purchased 8.2, and the kernel on that system causes exactly the same problems. Any suggestions? I also have the separate problem that the 8.2 version permits me to use DMA with my disk drives, but the 8.1 does not. I would like to have both DMA and 3D acceleration in one system if possible. Very perplexing. All suggestions welcome. Matt