Macbook Air 13" (Oct 2010) Locks up when connecting external display

Question

Since I installed Lion my Macbook Air needs to be restarted nearly every time I connect an external display.   This did not happen prior to Lion and wondering if anyone has a solution.
Details:
- 13" Macbook Air (October 2010 version)
- Dell 27" LCD display
- Mini-Displayport <-> Displayport cable used to connect

Answer 1

OK. It was a guess anyway.
I changed my screen resolution and then did a search of system files to see what was changed today.
I sorted by descending date/time and that file was at the top of the list.
I opened it with the Property List Editor program and saw it contained the changed resolution, so I took a guess that deleting that file and rebooting would set you straight.
You might look for recently changed files with likely names in your personal settings folder:
~/library/preferences
and try deleting and re-logon (you don't need to restart if you're only changing your own files - a re-logon picks up the change)
Sorry - I don't have a better guess. Good luck