Ubuntu 12.04 64-bit
Intel Core i3 540
AMD ATI RV710 [Radeon HD 4350] - graphic driver
I have tried to figure out what is causing the freeze, but I have not found it. It typically happens when I browse in any browser to websites with flash content or are rich graphically. It also freezes when I use VirtualBox, and I have had a lot of difficulty installing different distros in VirtualBox. I have managed to install after tweaking VirtualBox, but it still freezes the whole system.
I have tried both to use the proprietary graphic driver and without using it, both ways it freezes.
When I was running Ubuntu 10.04 before, everything worked fine until after I installed Ubuntu 12.04. I have put more memory in between, but running memtest did not find any errors.
Regarding browsers, Chrome was the worst browser, so I have uninstalled it. Opera and Firefox still crash.
I have tried Ctrl + Alt + F1 - no response.
I have tried Alt + SysRq + REISUB slowly - no response.
What happens is that the screen locks and there is no response from any device. The only way to get it running is to push the reset button on my computer.
It actually froze when I was using the Firefox spellchecker (right mouse click) on this question.
So how can I get a stable system? How can I find what is wrong and fix it?