Guns,

Does the web.config file get changed? Probably because of a virus scanner?
Or do you prob. have another file in your bin directory which is changed
during execution or another configuration file or an access database?

If so you know why your application will restart and (because you save the
session InProc) looses your session.

Greetings

  Daniel

Try instead of "InProc" this:

 <sessionState
  mode="StateServer"
  stateConnectionString="tcpip=127.0.0.1:42424"
  stateNetworkTimeout="10"
  sqlConnectionString="data source=127.0.0.1;Integrated Security=SSPI"
  cookieless="false"
  timeout="20"
 />

And run the "ASP.NET State Server Service" in Services....

I had the same problem of ramdomly disappearing/reappearing
session-values.... Not it works fine.