I am getting infrequent incidents when the session variables for one client become null or an "invalid viewstate" error or an "Invalid character in Base64 string" is reported.
Other clients running at the same time are not affected, and the user with the problem can restart and does not get the error the second time.
(According to the server log, the app is not being shut down or recycled, and it runs in its own app pool on a VPS)
As this is a public site I can't mandate that users have cookies enabled, so my web.config shows
<sessionState mode="InProc" cookieless="AutoDetect" regenerateExpiredSessionId="true" timeout="60"/>
How can session variables be destroyed without causing an app recycle?