Ubuntu 9.10 upgrade problem

My main ubunutu machine is a dell precision 470 with two dual-core xeon 3.2ghz cpu's, 3 gig of ram, terabyte hd and an nvidia pci-e video card. It ran 24/7 without problem since ubuntu 7.10 but when i upgraded to 9.10 a very perplexing problem occurred.

I did the upgrade from the upgrade manager and it went fine. However, i later noticed the machine had hung. Totally frozen and could only be restarted by unplugging the power cord. This happen the next time so i started keeping track. The symptom was that when the video went into power-save mode you could not get the display back and from there the system then froze up. I had to build an emergency ubuntu machine with a dual core 3.0ghz P4 - the difference in speed is so great this is not a long term solution. With a dual cpu machine you never have to wait, a single cpu is so much less usable. For example, on the dual xeon box i can start a 10-20 gig file copy, burn a DVD and read the mail without any lag, on the single cpu such a file copy operation causes a noticeable lag with windows and mouse operations.

Anyway, suspecting the power save settings i tweaked them in various ways without success, even setting the system to never enter power save mode. I upgraded the bios to the latest version but no joy. I then pulled the hard drive and stuck in another and installed windows xp. This ran ok for a day and then exhibited the same freezing problem with the video. The video card is a PNY nvidia one. So i put back the ubuntu hard drive and disabled the nvidia binary driver. No joy there. Finally, i removed the nvidia card and replaced it with an ATI video card.

The system has now been running perfectly for 24 hours without a hiccup. I also noticed that it is quieter - the fans used to run a lot before and now they do not. This may indicate the video card was putting out lots of heat.

So what did we learn. Perhaps the upgrade from 9.04 to 9.10 did not cause the problem, it may have been a coincidence. The fact the video card had the same blanking problem under windows would seem to indicate this is the case. Anyway, nothing was lost since data is not stored on the OS drive anyway (a good idea - never store your data on the same hard drive as the OS) but i am glad to have the faster machine back...