Problem with IE and new online shop

[katica]

Am constructing a new online shop with a shopping cart. Am having a problem with Internet Explorer that is not happening with Mozilla Firefox. When testing the online shop, and going in to purchase the first item, it adds to the shopping cart. On clicking on Continue Shopping, most times we get a popup message saying 'Windows Internet Explorer. Internet Explorer cannot open the Internet Site, web page address is given, followed by Operation aborted' and then we get a page saying 'Internet Explorer cannot display the web page....' When I use the back button, I can usually get the page back. When I try again to add the item to the shopping cart, it says Web Page has expired. Click on the back button again and page comes up and I can then add item to shopping cart. Go to add another item and it may or may not have the same issue. My web designer cannot figure out what the problem is. The web hosting people say the problem is not from their end.

My concern is that most of my customers use Internet Explorer. Can anyone help in this matter. Will be very very grateful
Thanks so much