I ran into this issue several times now. After installing a new Forefront Threat Management Gateway (TMG) 2010 when the TMG Console is started the first time it fails with the following error:

An error has occurred in the script on this page.
Line: 283
Char: 13
Error: invalid argument
Code: 0
URL:file:///C:/Program%20Files/Microsoft%20/Forefront%20Threat%20 Management %20Gateway/UI_HTMLs/Generic.htm?guid=%7B43E06AFC-729B-8BC2-33A9E35BB12D%7D
Do you want to continue running scripts on this page?

This is a small bug in HTML interface code. To solve it, navigate to the C:\Program Files\Microsoft Forefront Threat Management Gateway\UI_HTMLs\TabsHandler\ directory and open the TabsHandler.htc file.

There are 3 lines containing “paddingTop” causing this issue. Find the lines and disable them by adding // at the beginning of the line.

Save the file and the console opens as expected.