Resolution of display dropped to default size
 

I had good display resolution for a while after installing Ubuntu 10.04, however it changed to a default size of 800x600. I cannot adjust it any higher than 800x600 in display settings. I am using a Samsung Syncmaster 2243 display.
Video is a Radeon HD6450 and motherboard is MSI990FXA-GD80.
How can I troubleshoot the display?
Thanks

Look in /var/log/Xorg.0.log , which is the last session.

If it's a regular issue, drop to console runlevel in /etc/inittab and use startx to boot X. Many folks (myself included) run that way all the time.

It seems to be the Linkskey KVM. I found that by connecting the VGA cable directly to the monitor. Then shut down and pop in a different video card forces Ubuntu to re-register(correct word?) the video. I shut down again and put the original video card back in and all resolutions are available as before.