I’ve downloaded and installed NVIDIA 260.19.21 and restarted my X. Strangely, my KDE 4.5.3 was starting fast and stable. It also became stable. I guess KDE 4.5.3 and NVIDIA 260.19.21 on Gentoo x86_64 is a good combo.

Btw, I’m using NVIDIA 9200 onboard chip.