Note: All the other pages don't have the sliding side panel in place yet, this is only a test.
The sliding side panel can be found on the page "side_panel(test).html", which is only included on the sitemap thus far.
Any ideas, assistance, links, or whatever will be much appreciated.
I tested it on IE6 and didn't notice the bg images reload, though my computer is only about two years old. It works fine on Mozilla too. It sounds crazy, but when was the last time you purged the IE cache?
Also, it could be a combination of an IE bug / Video driver issue. Maybe a slow refresh rate for the monitor? Try a lower resolution and faster refresh rate and see if you get the same results.
I've got a slower Win95 computer at work with IE5.0 on it. I'll see if I can replicate what you describe on that.