Using Virtuemart 2.0.2 stable on Joomla 2.5.1.
Following Problem occours: When doing ajax-requests multiple times (e.g. adding product to cart than adding the same product again) in IE9 the ajax requests are cached so that the cart-module does not get updated. (See attached screenshot)
Suggestion for a solution: Just add a parameter with a random value to the ajax-requests.
[attachment cleanup by admin]