With the proprietary driver of my Radeon graphics card activated, I tried to set up a two-monitor display arrangement ("show same image in both monitors" unchecked), but the system gave the following error message:
"Required virtual size (2560,1024) does not fit available size, min. 320,200 max. 1600,1600."
Curiously, this problem does not occur when the Radeon driver is left unactivated.
Is there a way to adjust those parameters that are causing a problem, so that I could set up a two-monitor desktop?