The way that template is set up, you've got a lot of "borders" (actually "cellpadding") and when you put it on a 800x600 resolution you can only scrunch them down so far before they run up against that store window, which, according to the code, will only scrunch down to 752 pixels before it says, "I've drawn my line in the sand." Just experimenting, I arbitrarily changed that width down to 700px and the problem is solved, BUT...I wouldn't use that in a listing until I cleared it with Auctiva, first. As John Fogerty sang, "...for there were many things I didn't know." And there's got to be a simpler way, anyway.
I got something else up my sleeve and I'll be back. Stay tuned.