. About AGP error.
I've learnt that in order to try with nvidia-provided AGP support I need to remove agpgart
from being loaded on strtup. I did that and set NvAGP=1.
Now, I don't have Failed to verify AGP usage
warning in XFlog file and AGP support seems to be working ok:
~$ cat /proc/driver/nvidia/agp/status
AGP Rate: 2x
Fast Writes: Disabled
Previously it was disabled
Unfortunately, that didn't solve the problem: both glxgears
hangs the whole system completely. I'm getting tired with this...