WMM Import Error with DVD Shrink 3.2 Movie Files?

I'm using the program DVD Shrink 3.2 to extract movies from DVD on to the computer. And I'm trying to edit them together in WMM because the program splits the whole movie up in to different parts. The problem I'm having is, some of the part get this error message: "could not be imported. Unspecified error." and yet the other ones import fine. I change them all to the same type of video, and I've tried different formats like .mov, .avi, .mpg, .mpeg, and it doesn't work for those few certain files that won't import. Are some part of the movies corrupt? Is there any general suggestions on how to fix this? Is DVD Shrink not a good movie ripping program? Any advice would help!