We've just solved a highly perplexing issue on a recent project. Mysteriously, our lovely transitions on a Views Cycle banner rotator were not happening in IE7 and 8! Instead of smooth dissolves, the images transitioned suddenly with no effect.
Finally he tracked it down to the IE stylesheet, which I had used to solve a bug of extra space below the linked banner image. I see this a lot, and my preferred fix has been display:block on the "a" tag surrounding the image. But in this case, no good, since display:block apparently conflicts with the jquery that gives us the nice transitions.
After another search I found a solution for removing the space. On the image itself (rather than the a), "vertical-align: bottom" seems to work perfectly. I'll probably use this method from now on.