Having any problems in your TMG installations? Check out Rollup 2, it might just have the fix you are looking for.
http://support.microsoft.com/kb/2689195
KB number
Title
2701952 (http://support.microsoft.com/kb/2701952/ )
FIX: "Access is denied" status error when you use a delegated user account to try to monitor services in Forefront Threat Management Gateway 2010
2700248 (http://support.microsoft.com/kb/2700248/ )
FIX: A server that is running Forefront Threat Management Gateway 2010 may randomly stop processing incoming traffic
2700806 (http://support.microsoft.com/kb/2700806/ )
FIX: connectivity verifier that uses the "HTTP request" connection method may not detect when a web server comes back online in Forefront Threat Management Gateway 2010
2705787 (http://support.microsoft.com/kb/2705787/ )
FIX: The Firewall service may intermittently crash when it processes client web proxy requests in a Forefront Threat Management Gateway 2010 environment
2701943 (http://support.microsoft.com/kb/2701943/ )
FIX: Error message when you try to join a Forefront Threat Management Gateway 2010 server to an array: "The Operation Failed. Error code - 0x80070002 - the system cannot find the file specified"
2705829 (http://support.microsoft.com/kb/2705829/ )
FIX: The Firewall service may stop responding to all traffic on a server that is running Forefront Threat Management Gateway 2010
2694478 (http://support.microsoft.com/kb/2694478/ )
FIX: Dynamic Caching may incorrectly delete recently cached objects from a caching server that is running Forefront Threat Management Gateway 2010 or Internet Security and Acceleration Server 2006