I am making this a community wiki, for three reasons:
I was having a problem where the div below my header in the accordion, which had a white background over a blue page background, had its background-color disappearing. Sometimes when hovering over another header element, it would show up; sometimes when highlighting text, it would show up again too. It was very strange and ONLY HAPPENING IN IE7.
Applying zoom:1; targeting only IE7 on the ui-content div fixed this.
I hope that helps someone because I just spent several hours trying to track this down.