Back doing web development at the moment and it is taking me a little while to get back up to speed.
Anyway for the project I am working on decided to create an HttpHandler as a Front Controller. All well and good until I tried to use the session state. Couldn't access it from the Handler or pages that were called through to. Bugger! Turns out you need to implement the IRequiresSessionState interface for the HttpHandler if you want to use the sesssion state.
You learn something new everyday.