iMovie - Importing MP3


Did a search and didn't find a complete answer BUT:

Was there a specific reason that iMovie on OS X isn't importing a standard .mp3 file? By "standard", I mean those that aren't necessarily ripped by iTunes...

Of course, if I convert to AIFF or reconvert to .mp3, then iMovie imports it no problem!

Thanks in advance.

For those interested, I posted pics from the recent Tokyo Motor Show 2001 ...