The code Thread.CurrentPrincipal as IChatPrinciple) returns null. IChatPrinciple extends IPrincipal, but a conversion error still occurs. I've been upgrading my application from .net 2.0 to .net 4.0. The .net 2.0 app did not an issue with the code, and I'm at a loss as to what IIS (version 6) settings could be causing this. Any help would be much appreciated. Thanks.