When you use Forms Based Authentication (FBA) in a Microsoft Forefront Threat Management Gateway (TMG) 2010 environment, you may be redirected to the password change page even when your password has not expired or is not near expiration. This behavior may occur when the password expiry policy is controlled by a Fine-Grained Password Policy (FGPP) or by Password Settings Objects (PSOs).
This problem occurs because TMG does not check the PSOs object class for the user and relies on the Domain Security policy. This may cause TMG to incorrectly calculate the password expiration time.
To resolve this problem, install the service pack that is described in the following Microsoft Knowledge Base article:
2555840 Description of Service Pack 2 for Microsoft Forefront Threat Management Gateway 2010
Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.
For more information about software update terminology, click the following article number to view the article in the Microsoft Knowledge Base:
824684 Description of the standard terminology that is used to describe Microsoft software updates