During the installation of Microsoft Forefront Unified Access Gateway (UAG), Microsoft Forefront Threat Management Gateway 2010 (TMG) is installed first. At the end of the TMG installation, the Fweng.sys driver is loaded and started. When the driver is started, the server crashes with the following Stop error code:
DRIVER_IRQL_NOT_LESS_OR_EQUAL referencing fweng.sys.
This issue occurs when a network adapter driver forwards a zero packet size to Fweng.sys.
To resolve this issue, install the software update that is described in the following Microsoft Knowledge Base article:
Software Update 1 Rollup 4 for Forefront Threat Management Gateway (TMG) 2010 Service Pack 1
Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.