I had the same problem as you Jim and the problem is indeed an IE issue. It seems that as soon as it take more than a couple of seconds to connect to the site the error occures. I have a modified product_info.php with lightbox and some own code also, and I could see on your site that at least lightbox was added. I tried in auction_bids.php to remove this function:
window.location="<?php echo tep_href_link(FILENAME_PRODUCT_INFO,'products_id=' . $this->auctions['auctions'][$this->auctionKey]->products_id . '&page=' . (int)$_GET['page'] . '&auction_show=1'); ?>";
and it helped a lot it seems at least.
I cant see why the Redirect should be there maybe FWR Media can explain this. None of the functions of the addon was affected as far as I can see. An really good addon it is FWR and the plan is to go live with this addon in a few days, I will post the link to the site then if I am requested. Good luck to you Jim and to all oscommerce workers here. Great job FWR Media!