Problem With UpdateProgress Control

VS2005 C# w/AJAX Extensions

I added an update progress control to my web page. Initially I used
some plain html and text in the control's section,
and that worked well. Then I needed to be able to programmatically
control an image's src property (just once during load)...and so I
changed the html img tag to an asp.net server control tag.
That's when everything broke! Now each time I try to compile I receive
an error...

[MyPageClass] does not contain a definition for [MyServerControlID]

....It's as if these server controls are "invisible?" inside of the
update progress control. Can anyone offer any ideas on what's going on
here?

JP