Xfce 4.6.0: Cannot change display resolution

[Angel Tsankov]

Hello.

I have an LCD display with a maximum resolution of 1280x1024.  I already got 
X to run at 1280x1024 but now I cannot change to a lower resolution within 
Xfce 4.6.0.  When I go to 'Display Settings' and select some other 
resolution (for example 1024x768), after I click 'Apply' nothing happens. 
What could be the reason for this?  Is there a log file that I could 
examine?

Regards,
Angel Tsankov