Just thought about sharing this tiny bug fix:
So here is our situation, we got steam uptodate, all graphic driver updates, same for motherboard, etc, all fixed and running but for some reason hl2, hl2 dm and other source games keep locking up at the “loading…” screen. The menu just doesnt show up. Same happens if you join a server directly.
The core problem is related to your automated firewall in xp/2000.
Tag "xp"