IIS Service Provider Problem

[Russell J Yount]

We have an IIS server which at times fails with a Shibboleth error screen of Attempted to insert duplicate storage key. 

Restarting the web server corrects the problem.

The Shibboleth log file looks like:

2012-01-10 13:24:47 WARN Shibboleth.SessionCache [8404] isapi_shib: client address mismatch
2012-01-10 13:24:47 WARN Shibboleth.ServiceProvider [8404] isapi_shib: error during session lookup: Your IP address (X.X.X.X) does not match the address recorded at the time the session was established.
2012-01-10 13:24:47 ERROR Shibboleth.Listener [8404] isapi_shib: remoted message returned an error: Attempted to insert duplicate storage key.
2012-01-10 13:24:47 ERROR Shibboleth.ISAPI [8404] isapi_shib: Attempted to insert duplicate storage key.
2012-01-10 13:24:48 ERROR Shibboleth.Listener [8404] isapi_shib: remoted message returned an error: Attempted to insert duplicate storage key.
2012-01-10 13:24:48 ERROR Shibboleth.ISAPI [8404] isapi_shib: Attempted to insert duplicate storage key.

[last two messages repeated many times];

(I have substituted X.X.X.X for actual client IP address.)


Is this a known bug? How should we approach tracking the cause down?

-Russ