Today on deploying custom pages within CRM, if found out that my drop down control was not working properly. On initial page load the drop down control was showing all the values but once the page is posted back it was showing no items inside it !
It happens becuase by default view state is disabled for pages within CRM 4.0
These are settings for the web.config within CRM 4.0
pages buffer=”true” enableSessionState=”false” enableViewState=”false” validateRequest=”false”
So just make sure if your pages are making use of view state or session state, ovverride the above settings for your custom pages!!