System crash and freeze - reboot on terminal

I have an issue on my laptop, probably the bigger I never had!?!
I use:

Ubuntu 12.04 64bit - 3.2 kernel
Nvidia 8600M GT
drivers 319, but tried 304 and newer from x-swat repo and nouveau

Since two weeks, system crashes often, with different symptoms, all are system freeze and need hard reboot: screen becomes grey after sleep, or pics (like wallpaper) becomes suddenly like ‘EGA’, or just ‘regular’ freeze.
I was already a “freeze victim” (many posts seems to report this bug), mostly when changing workspace. But now, when I reboot, X doesn’t start any more. I have to try many times in safe mode, (safe x doesn’t work), then some times it works. I’m getting kernel panics, error messages, psychedelic colours… and then sometimes I have my desktop back… until next freeze.

Something very strange occurs when I boot after crash: I get some display bug on computer start, like lines and points appearing shortly before grub, and more visible in bios config screen: it appear shortly ~once a second, or when I press a key.

Something else important: I can’t either boot on other distribution (I have 3). Problem occurs in different way, but doesn’t start.

Some relevant error messages I found in logs:

fatal server error: no screen found
When I dpkg-reconfigure x, something like: number of screen doesn't match number of device found (never found this message in logs)
NVRM: GPU at 0000:01:00.0 Has Fallen Off The Bus

investigating on this last error, it seems it could be hardware issue.

I just want to be ABSOLUTELY sure it is hardware before I consider to buy a new laptop: it’s 6 years old for sure, but if I can save it… and money…

I post the bug-report asap…

Thank you in advance

This is the bug report after freeze and reboot, in terminal. Doesn’t seem to have completed. I get 2 error saying: impossible to open /dev/nvidia… or someting.
The ‘old’ one is when system works.
[This file was removed because it was flagged as potentially malicious] (48.2 KB)
nvidia-bug-report.log.old.gz (67.3 KB)

At the moment, the only way I found to run a stable desktop is in vesa mode, but resolution is very low… no way to increase?