I was just fooling around with FCE again and I kept getting a strange problem. Whenever I would add a cross dissolve between 2 clips, I would get a few frames of a previous clip with the same type of CD either in the fading out of the old clip or the fading in of the new one, and it would be a clip that was not immediately before or after it, it would be from the beginning of the timeline. It's not in the order I filmed it when it happens either. I have no idea why it keeps happening, I am opening a new transition in the editor and setting it up each time. I was able to correct the problem by roll editing a little, but it's still pretty strange. Also, the cross dissolves wouldn't work on some clips, but they would on others. First time that's ever happened too.

Delete all your render files. SOme of them might have gotten corrupt.

for the part about it working on some clips and not on others.....there has to be enough footage for the cross dissolve to work. Basically the two clips you use need to overlap enough in order make the cross dissolve....dissolve. Hope this helps.