I am very new to K2, and I find it a bit overwhelming, but I hopefully I'll get the hang of it.

Take a look at my site:
in FF and then in IE9.

In firefox, the K2 Content module appears correctly with XSmall images. But in IE9, the images are the wrong size. Is that a bug? Or am I missing something?

Thanks for your help.

Hi. This has nothing to do with K2. K2 will serve the same image two both browsers. It seems that you have another extension that manipulates the images when the page is loaded.