I don't know if this will help but it's worth a try.
I couldn't get MJ to import any of my mpeg movies, but I was able to right-click them and add them to playing now. Once they were in playing now I could right-click again and import to library from there.
You can obviously select a heap of files this way, I did about 400 mpeg movies in 4 lots but I probably could have done them all in one go.
Another trick I do sometimes (especially with kazaa downloads) is to change the file extension. Some applications don't seem to care whether the extension is accurate or not, as long as it and the file itself are both supported by that application.
(In case you don't know, to change file extensions go into tools>folder options>view and make sure 'hide file extensions for known file types' is unchecked then just rename the file with the new extension. At least that's the process for win2k)
Best of luck,
FB