This occurs in Maverick and Natty. Single screen is fine, mirror of single screen is fine. If the mirror box is unchecked and the second monitor is turned on to extend the desktop then all windows are greyed out (like they do when a process has timed out and is unresponsive) and pop up menus are greyed out but icons, panels and background are fine and the windows do operate (just can't see them well enough to use)
I have a D620 with intel graphics. This machine did work with dual monitors at some time in the past, however I have been using another machine, a D630 with nvidia and it works fine. Yes, there have been any number of updates. I also upgraded from Maverick to Natty to see if it would go away. No joy.
Also, the D620 has a dual boot windows system and the windows xp system works fine with daul monitors
There is a forum thread that goes into more detail and there are a number of users experiencing this problem.
Thread: greyed out windows
Thanks for reading