Ajax Combobox not handling display:none correctly

I have an Ajax ComboBox in an asp:panel.  The panel has a CssClass="hide" assigned which includes "display:none".  

The user can click on another element that fires a JavaScript function which sets the panel's CssClass="show" which includes "width:100%".  This causes all controls in the panel to displayexcept the arrow image on the ComboBox

IF I set the panel to start life with CssClass="show" everything displays correctly.  I can then use that function to change it to CssClass="hide" then back to CssClass="show" and everything still looks correct!

Thoughts/Suggestions?