I like to host asp.net web application in IIS 7.0 (windows server 2008).
I configured session state as sessionstate mode=\"inproc\" timeout = 120. Even the session
Had nearly same problem with HTTP handler written in C# using SessionState. Seems the property IsReusable should be false otherwise I was running in the problem of session loose.
Thanks Mmerrell for his Response, which brought me on right track.