Why do you need two games running at once? Games kinda want as much resources as possible.
It's not an issue of PC resources. For some reason it causes a bizarre server conflict.
And I am trying to watch a dota match while playing TF. Also I almost always have Dota running while I wait for parties to form and it's nice to have some other game to play while I wait. Looks like TF won;t be that game. Ah well.