I think I found out what was going wrong, updated in first post. Please post output.
It wasn't RC5pre11 fault, sorry. Apparently, since the move from 915resolution to nvidia_resolution, structures needed to be packed (that's the 9 bytes long struct with a size of 10 problem). So now, according to the little virtual patcher I've set up, it should be working, dynamically counting modes etc... hopefully without crashing everything.
I don't know how comes it worked without that before and stopped working after a code move.
It implied little changes in Intel part I can't test, can someone with a GMA test if modes are patched ("1024x768 -> 1024x640" messages) ?
I hope it finally corrects the nvidia part, sorry about that guys.