Unable to save converted file in Windows Movie Maker

I recently purchased Converter 3.6. I used it to convert a Real Player FLV file to a WMV file which I clipped in Windows Movie Maker 2.6 and then saved the movie file. All worked okay.

But today I performed the same process on a different file and Windows Movie Maker is saying it is unable to save the file. Yet, if I convert my original FLV in Real Player Converter, clip it in Movie Maker, and then save it, the file is saved by Movie Maker.

I also converted a different Real Player FLV file and had the same problem with it.

What is wrong?