I'm experiencing exactly
the same problem
when I type startx from console, the machine is under hardware lockup for five long minutes, not even answering to network (ssh, etc...), then the nvidia splashscreen appears, and everything works OK.
I am running the 2.6.5-gentoo-r1 kernel, with a "01:00.0 VGA compatible controller: nVidia Corporation NV20 [GeForce3 Ti 500] (rev a3)" graphics card, and have the following options in /etc/X11/XF86Config :
# Load "dri"
Identifier "GeForce3 Ti500"
Option "NvAGP" "1"
I have also disabled AGPGART (/dev/agpgart) support in kernel because it caused errors in `dmesg`, but it didn't solve the problem.
I was running FreeBSD before, with nvidia drivers version 4365, and had no problem.
I tried under Linux 2.4.25 and Linux 2.6.5, with nvidia drivers version 4496-r3 and 5336-r2, in vain...