EDIT: Problem solved updating to 256.44.
When I resume from suspend to RAM, X isn't able to start.
The keyboard becomes unresponsive, but I can ssh from another comp and generate the bug report.
These are the last 2 lines in the Xorg log after the resume:
[ 293.364] (II) NVIDIA(0): Setting mode "CRT:1024x768_85+0+0,DFP:1680x1050_60+1024+0"
[ 298.367] (EE) NVIDIA(0): WAIT: (E, 0, 0x827d, 0)
AFAIK the other devices are resuming fine. In runlevel 3 (console) suspend to RAM works OK.
Any ideas? Should I try a previous driver?