Are you **sure** that this is a problem on the server side in extracting the value from the request - and that it could not be a client side problem in formulating / sending the request in the first place?
Have you tried looking at what actually goes over the wire with something like WireShark so that you can be 100% certain whether you need to be looking at the server side or client side code?
Have you also looked at the page life cycle and checked the state of things in its various stages - see
http://msdn.microsoft.com/en-us/library/ms178472.aspx[
^]. If you've checked that this is a server side problem, handle and debug into page events to see what the HttpRequest object is actually giving you - are other (standard) headers / form variables visible? Where in the life cycle is your current code executing?