I have a user control that contains only a text box and on another form I add this user control dynamically, a user can add the user control many times. I use a session vari
I've had the same problem in the past.
What I did was give the dynamically-added control an ID, and made sure it retained that ID also on postback (in my case, I kept all the information in the session, and re-created the controls).
Once the postbacked control has the same ID as as before, Microsoft did magic and refilled the controls with the pre-postback values.