RHEV UserPortal shows HTTP 500 error

Issue

• The UserPortal sometimes produces the following error:

A Request to the server failed with the following Status Code 500

• At the time of the error the UserPortal was only opened, not used (no clicks, just the auto refresh).
• In this case the UserPortal was opened with Internet Explorer 9 on Windows 7. The error has been seen on WinXP with IE8 as well.
• The SPICE session does not quit and on a page refresh the UserPortal is accessible again, but this can confuse users.
• The error appears with and without a VPN.