When migrating from Internet Security and Acceleration (ISA) Server 2004/2006 to Threat Management Gateway (TMG) 2010 you may run into this error 0xc00403a4 in importing the ISA configuration to TMG.
The file cannot be imported. The exported file contains an object of type Policy Rules which cannot be imported into an object of type Array.
The error occurred on object '<TMGServerName>' of class 'Array' in the scope of array '<TMGServerName>'.
Go back to your ISA Server installation and re-export the ISA Configuration. Make sure Export Confidential Information as well as Export User Permission Settings are selected. I am not 100% sure if User Permissions are needed (when configurations are changed from Domain to Workgroup, that is, ISA in deployed in Domain and TMG deployed as standalone)
Get the configuration file and certificates copied over prior to TMG installation. Once TMG is installed network communication will be limited (blocked by TMG rules). If it is already too late (TMG is already installed), stop the TMG Firewall Service, copy over the files and restart the service.