I've got a big problem that's preventing me from testing my maps. Here's the situation: I have a map ready to test in Hammer. I click "Run Map..." It seems to compile just fine. The problem comes when Steam tries to run Team Fortress 2. I get the following message: "This game is currently unavailable. Please try again at another time." It happens every time. I even tried closing Hammer and just plain running TF2. I got the same message since I still had Source SDK open. So I tried opening Hammer and closing the SDK window. Same result. Finally I closed both and ran TF2 normally. Worked just fine. Does anyone have any idea of a possible cause of this problem? Or perhaps even how to fix it?