I've been playing with Greg's new advanced search code, and I ran into two problems in IE7. I've fixed both issues, but I'm describing my fixes here in case anybody has better ideas or concerns about negative side effects.
1.) In both classic and default templates, the display was garbled. In classic, text boxes were completely invisible!
Fix: I set a 96% width on a high-level <div> tag wrapped around the main area of the page. This explicit width seems to help IE render correctly and only changes the output of other browsers by a few pixels.
2.) If you added a bunch of groups and then tried to remove them, you would end up on an error page.