How can I get Movie Maker to RE-FIND a video file used in a movie I've just spent over an hour editing?

The video file has NOT changed locations or names, and Movie Maker had absolutely no problem finding the file right until I tried to "Save Movie."

When I tried saving the movie, both video files were located in the SAME directory and were the same .AVI format. While saving the movie, it successfully saved the movie up to the start of the second video file, then crapped-out with an error message reporting it was unable to find the video file.

After the "Video file not found" error, on the editing screen, it still shows clips of the first video, but only shows exclamation points as "frames" for the second file clips, but the playback window is still able to flawlessly play the edited version of the reportedly "not found" video file.

How can I get Movie Maker to recognize the correct video file that is still in the same location and still has the same name it had the first time it was placed into my project?

Before you tell me anything about it being related to Movie Maker not working with Windows XP... The computer I'm using it on has Windows 7 Professional on it, and also has more than 8 Gig Ram available on it.