This is one of the most common problems of SP1. Sa shellstyle.dll ang problem nito. Try mo yung suggestion ni Chris. If this does not work, try this:

1. Go to your folder where your themes are located (usually nasa C:\Windows\Resources\Themes yung mga themes).
2. Open the folder of the theme you are currently using.
3. Locate then open the folder named 'Shell' on the previous directory. Inside you would find the file 'shellsyle.dll'.
4. Rename this folder where this file resides to the name of the theme you are using. Example.: your current theme is named 'Alpha' the you should rename the 'Shell' folder to 'Alpha'.
8. Re-apply the theme.
0. Finally, go to Add/Remove programs.

Hope this helps.