imac screen problem on startup/shutdown

[photomel]

I have screen problems with my 9 month old imac only on start up and shut down. I have attached a screen shot. I goes away once I open up a window and my normal desktop image appears. I have tried the diagnostics and different desktop images......still happening. Any ideas?

[joelw135]

I have screen problems with my 9 month old imac only on start up and shut down. I have attached a screen shot. I goes away once I open up a window and my normal desktop image appears. I have tried the diagnostics and different desktop images......still happening. Any ideas?
Try following the directions below.

To get rid of the corrupted plist file: Open your hard drive icon, open the Users folder, open the "Home" folder (your account's folder), open the Library folder, open the Preferences folder, and then find the "com.apple.desktop.plist" file and move it to your desktop. Restart your machine, log-in, and hopefully your problem is gone. When you login, your desktop pic will have been replaced by the default "Aurora" picture. You can then trash the plist file you moved to your desktop.