I have a dot net nuke site that I have written a custom module for. It a form that users fill out to submit information - no big deal.
On the form, I use the Ajax and the Ajaxoolkit for validation, and a calendar popup. I enable/disable controls based on form data.
Everthing works well in every browser/OS combo that I have tested EXCEPT IE7/Vista.
The page renders with most of the lables and conrols invisible. The controls are there and you can even enter data, you just can see them.
Here is a link: http://www.gpusbc.com/test/tabid/76/Default.aspx
I develop on a Win XP machine with IE7 and FireFox and there are no problems. FireFox on Vista has no problems.