User control partially renders in UpdatePanel

hi all,

I have a custom user control (lets call it MapControl) that uses ESRI Javascript API (also uses dojo) to load a map into a div, I also have some other Asp.net controls with it. When I load my MapControl on any page it works fine, if I add it within an UpdatePanel it also works fine, BUT if I add it to an "invisible" panel then after some button clicks change that invisible panel to visible, the map control does not load completely! The ASP.Net controls loads fine, but my div containing the map does not! I've been trying to solve this for a couple of weeks, and no luck so far. If I add a button within the MapControl panel that do a postback it works fine after the button is clicked.

How can I solve this issue without having to use the button?

Any help, comments, or suggestions are much appreciated

Thanks

Jafar