unable to switch to console mode

[clemmy]

hello, I've got a problem with x86_64 nvidia driver 171.06 and ubuntu
8.04 (kernel 2.6.24-12-generic)

After running X i'm not able to switch back to console mode:
Ctrl+Alt+Fn gets me to a black screen, with backlight on, but nothing
displayed. Same problem with 169.12 drivers.

No problems running X with nv opensource drivers.

I've read in the readme.txt of nvidia drivers about problems with
rivabf, but i think i'm not using rivafb, it's not listed in my lsmod
nor in my dmesg

what can i do to solve this problem?

I wasn't able to attach my nvidia-bug-report.log because it's exceeding forum's size limit...