Recently I noticed that on June 10th around midnight that Steam had an update. I was mapping until I noticed that I needed to update. So what I did was saved my work, closed Source SDK and clicked the restart steam button.
After steam loads up again, I go to run Source SDK, works fine. I try to launch one of the tools from Source SDK and I get the following Error on any game content:
"SteamStartup() failed: SteamStartup(0xf,0x0012F66C) failed with error 1: Failed create pipe: 6, Win32 Error 6 "The handle is invalid.""
After this error the first time, I restarted steam, loaded up source SDK and same result.