Working on a client’s OCS setup and got to the reverse proxy. Did my normal setup for the box and went about installing TMG 2010. Got to the end and it gave an error with the number -2147024891 and said to reboot the box. No matter how many times I rebooted, it didn’t matter, TMG services never started.

After many hours of trying everything I could think of, I tried the install with the machine as a stand-alone server and not a member of the domain. BAM! Everything went in smoothly. Evidently Microsoft wants you to use the TMG 2010 management tools to join the domain for some reason.