No thumbnails... wtf?

After installing Office XP (required by the company) my thumbnail previews don’t show up in the Windows Explorer anymore. Does anybody have any idea why this is? I need these thumbnails because I have to manage a whole bunch of graphics for the web site. The thumbnail previews for .FPX (Flashpix), and .GIF are still working, but the preview for .JPG is always looking like a text file. WTF is going on?!