Premiere Pro - Insufficient Media Error - Please help!

Hi, everyone!

I'm working in Adobe Premiere Pro (CS3), taking 3 thirty second video clips, and putting them together, along with an audio track, to make a 1:30 video background with music.

I'm trying to apply a short cross dissolve to each of the video clips. When I do, I get an error message that there is insufficient media and some frames will be repeated.

This is a mystery to me, because each of the thirty second clips is clearly longer than the cross dissolve transition.

The transitions seem to play fine in Premiere, but do not appear to show up in any render so far (I've tried .avi, .mov, and .wmv)

Any idea why I might be getting this error, and how I can correct the problem?