I've searched the forums and google but can't find any reference to this...
If I open a Zimlet of any kind (including Add Attachment, for example) in IE and the Zimlet happens to be longer than the current browser window then IE does not show the standard overflow scroll bar on the browser window. Firefox does.
I'm using IE6.
This came to my attention because one of my Zimlets has quite a lot of content and stretches off the bottom of the browser window. The overflow area then becomes inaccessable. As I say, the same thing turns out to apply to smaller Zimlets too if they are opened in a small browser window, which might be unavoidable on a netbook, for example.