How do I get .flv files to play in iMovie?

I already downloaded Perian, so I can play .flv files in Quicktime. However, I'm unable to import these into iMovie. Whenever I click the import button, the file I'd like to import is greyed out and I'm unable to play it.

I'm running Mac OS X, iMovie '08, Quicktime 7.4.5, and Perian 1.1.