I hadn't used the HtmlControls.HtmlInputFile control for a while, and was getting

"Object reference not set to an instance of an object." 

My form encryption type was correct, id name gibed, everything good.  Since everything was “right” I thought it might do a W2K3 thing. (Wouldn't be the first time...)  So a do a quick Existing Item copy to a W2K Server project and relaunch.  Same error.  Good!  Not a W2K3 issue. 

Reviewing the code again I saw that I didn't declare my HtmlInputFile control as protected! 

So I need to remember: when complexed, do a .NET 101 code check.