Windows Movie Maker Clip/Storyboard playback issue

[wazzle]

I am having a problem with Windows Movie Maker. It captured the clips just fine and they are all in .wmv format. Before I put anything on the timeline or storyboard, they play fine, with sound and all. But once I've put any clip onto the timeline/storyboard, the clips will not show up in the preview window to the right of the clips, and the timeline will not play. The buttons are not grey, but the clip will not show up, and when I click the play button I simply get the message "Class not registered". I tried that command prompt thing that works for most capturing issues, but when I quit and re-opened WMM, the same error still appears. Any advice? Please respond ASAP. Thank you.