I'm surprised I couldn't find this issue in the forum, but if it's been done before then my apologies.
I've been playing with the E-commerce Lite plugin and at first thought my problem was theme specific but it seems to have the same problem in kubrick also.
The problem is that when I add an item to the shopping cart the cart expands and overlaps the product description text, which looks pretty dodgy to say the least. Editing the CSS doesn't help as far as I can see.
I just realized that the issue seems to be firefox specific(perhaps opera too I don't know) but works fine in IE which is a first...
So I'm hoping someone has come across this and has found a cure?