Saving and Using Edited Clips as .DV files

I have successfully created IMovie's with chapters that I burned into working DVD's using IDVD. My problem is that I would like to save the edited clips I have made in IMovie as individual .dv files for archive purposes and to use in future IMovie projects. I have tried "Share/Quicktime/Selected Clips" and it appears to create a normal .dv file. But when I try to use the .dv file by dragging it into IMovie, I get the message:

"Error During Import
The file could not be imported: [name of file]

By the way, this was the method I was advised to use at the ProCare session I had yesterday. I have done a lot of forum and internet searching, but I can't find out what I am doing wrong. I would really appreciate some help.

Thanks.