Thanks for that. I add the form tag in but when I run the site, on the RADWindow which is throwing the bug, I now get a YSOD asking for me to put the RADScriptManager in the form tag. So I do this, but then I when I run my site, the webpage which was causing the error (called activities, added to a RADWindow on Default) keeps loading. Default is my standard start page. When I go to the Default page, none of the three RADWindows show up (visible and visibleonpageload set to true for all).
EDIT: All fixed but got 2 strange errors with the other controls. :) Where is an example of using moveTo to set the position of my RADWindow? I am assuming this is the client side method which will sort out the positioning. What parameters does it take?