I suspect that the problem is with the graphics driver.
ATI driver might be buggy.
I observed that making tasks with more graphical power causes system freeze more frequently. For example switching compiz on I obtain a freeze within a few minutes. Many times it occurs at suspending the machine. If I do not leave any application with extra graphical activity at suspend usually it is successful else not.
I suspect that the problem is with the graphics driver.
ATI driver might be buggy.
I observed that making tasks with more graphical power causes system freeze more frequently. For example switching compiz on I obtain a freeze within a few minutes. Many times it occurs at suspending the machine. If I do not leave any application with extra graphical activity at suspend usually it is successful else not.