All, I had the same issue and it also affected other preferences like Energy Saver and some others. None of the file deletions worked. But look at this solution from another user. Open System Preferences in 32 bit mode. Solved the desktop and energy saver access issues for me, thank goodness.
Could not load Energy Saver preference pane. <near bottom of first page>
"Found a solution that works for me.
Running Lion 10.7.5 in an MacPro 1.1 - machine is new to me, and is several years old
Deleted the various pref files as per above.
Reinstalled 10.7.5 combo update.
Still could not open energy saver preference pane. Machine was restarting at 10:25pm each night!!!
The solution - I found the system preferences app in the Applications folder
Get Info and selected - Open in 32 bit mode
Given System Information>Software>Preference panes says Energy Saver preference pane is 64 bit, I was sceptical this would work. But it does. At least I can now open my Energy Saving preference pane and get the Mac Pro to behave as I want it to.
Credit to Joseph Delaney in https://discussions.apple.com/thread/4142349?start=0&tstart=0
Tim"