Verifying, Verifying, Verifying... Good Lord!

Recently, Garry’s Mod REFUSES to start up without first doing a cache verification. Not too bad, I can just leave it for a moment and then come back. The real problem is that I keep getting a message that the Steam servers are too busy to process my request or something to that degree!

But… here’s something I discovered. I was able to get on Garry’s Mod once, and I noticed that L4D content hadn’t synced. I check off the boxes in-game, exit, then try to play again, and then it’s trying to verify!

Is there some L4D1/2 update that Garry’s not up to speed with?

Try deleting the clientregistry.blob file.

Reading that, I assume that Garry’s Mod has its own separate clientregistry.blob?

You assume wrong (As far as I know)

Just try deleting the clientregistry.blob file which is in the base steam directory, relaunching steam and letting it do it’s thing, and then verifying ALL your source games. If you’re having an issue which is manifesting in the L4D content, perhaps its worth checking L4D?