You wrote while ago:
" There is also a message saying "Screen(s) found, but none have a usable configuration", but I believe that always shows up if the nVidia driver fails."
Exactly this message i've got today while experimenting with nvidia kernel source. I forgot
to do a depmod -a , then it was working again.
BTW meanwhile i had success to force my Geforce into SBA mode by modifying the source a little bit.