Try running the "verify integrity of game cache". (You can do this by finding TF2 in your steam game's library, right click on TF2, click on "Proporties", click on the "local files" tab then click "verify integrity of game cache...")
Also, did you install anything recently like any anti-virus programs? Anti-virus programs can cause hl2.exe errors at times.
My guess is that its probably something to do with the recent updates but it wouldn't hurt to try and rule some things out.