Lightbox pop ups

I have had several users call and tell me that they cannot check out due to the fact that the Continue shopping Proceed to check out lightbox is not popping up.

I have check it on safari, firefox and chrome on my mac. It works correctly on all 3.
I checked it on firefox on a PC and it worked fine.
I then checked it on IE8 and it worked .

One of the people that could not get it to function is on IE9.

I was offered the recommendation that it might be due to a Javascript conflict.
I am not sure where to begin looking into that one so i thought i would check here and se if anyone else has had a similar issue and if the resolved it.

thanks in advance.

Also is it possible to run the solution with out Lightbox?

It's a strange thing, can you give us a link to your website ?

You can change the option "After a product is added to the cart" in HikaShop > Configuraiton > Checkout.