shaderapidx9.dll....

Ok, now this is making me crazy…i get some kind of weird error when i want to
start HL2 Episode 1 or HL2 Episode 2. Steam tries to start the game and i get the message from windows that the application has crashed and the reason seems
to be “shaderapidx9.dll”. This has never happened to me, i didnt changed my system or drivers, so what is causing this error all of a sudden? Ive googled through the net and people seem to have this same error, but i couldnt fix it so far!
It only happens to Episode 1 and 2, it doesnt occur when i want to start Half Life 2!
Any ideas how to fix this?

Have you tried de-frag the caches, perhaps its missing, maybe a re-install.

Re-installing works 90% of the time. Also verify the integrity of your game files. I don’t know what it does, but it sounds like it might help.

Founded in 2004, Leakfree.org became one of the first online communities dedicated to Valve’s Source engine development. It is more famously known for the formation of Black Mesa: Source under the 'Leakfree Modification Team' handle in September 2004.