Well, there is an easy way to find out:
I uploaded an app (profiler style) that checks all your calls to ensure that
control derived objects are never called from a thread that did not create
them.
http://www.gotdotnet.com/Community/UserSamples/Details.aspx?SampleGuid=3cba64b4-3765-49ba-8a05-11d247195e65

Looking for comments

button validation preventing click
Re: Embedding UserControl in Internet Explorer
How to create a RTF file?
Provider Properties + IExtenderProvider
memory issue.