systems hangs on switch users

Only recourse is hard landing and reboot. I suspect that it has to do with the graphics driver, but I am not sure. Any suggestion where to start looking?

Thanks in advance.

Switch off all screensaving? Maybe
Or try without any effects enabled?

Under Personal Settings -> Desktop? I unclicked “Start automatically”

I already have desktop effect disabled.

Anything else?

Tried Caf4926’s suggestion, but system still hangs.

The reason I think it is the graphics driver is that when it hangs, it shows the little x (rather than the mouse or the circle) as in sax setup, and the background is black with blue dots!!??

BTW my graphics card uses ATI HD 4850 (if I remember correctly).

Is it supported here
Graphics Drivers & Software

I tried to install that package once, and it completely broke my x server. In fact you help me recover from that. Take a look at this thread to refresh your memory.

But I can’t even find a driver in the ATI list for the GPU you quoted.

I must have tried to 4800 series; I don’t remember exactly. That may be the reason the x-server broke.