HL2 Won't Start! Launcher DLL Error

I just tried to load HL2 the other day since installing HLDM and the new SDK, and all of a sudden its not loading. I get the error message

"Failed to load Launcher DLL: the specified procedure could not be found"

I've searched around and a number of people are experiencing the same problem, but know one knows how to fix it. Does anyone here, in your infinite wisdom, know how to fix this frickin' problem?

There was a problem with corrupt GCF files earlier this week. Go to the
steam website and have your GCF's validated. (It's a link in the news
item about it).

Does anyone at all have a clue how to fix it?! Apparently quite a few people have experienced the same problem but it seems Valve is trying to stop it being circulated. Apparently somebody posted about the problem on the steampowered forums and it got pulled. There are also no reports of it in the support section, which i find hard to believe.

CS: Source and HL2DM work fine, but since I installed DM and updated the SDK HL2 has been completely f**ked, and its starting to really piss me off!

Also I've validated the GCF files for HL2, HL2DM and the SDK, but that didn't work at all.

Well you could always delete them and start over :wink: I dunno, validating them should have worked...and usually if there's a problem with the SDK being corrupted, you run HL2 to FIX it (rechecks the cache), but if HL2 isn't running...can't really help you there.