From gamservers support forums:
Nothing is working right now. You cant connect through the search key, force connect, and the servers aren't showing up on the groups list.
There isn't anything anyone here can do about it right now. You can connect through HLSW. I played a whole game with bots and no one else connected. So, I assume only yourself and others with HLSW admin can connect to play together.
What's even more annoying was that there was a 2nd update the same day the new DLC was released that fixed the problems. Then the next day they released another update that screwed it all up again...
It's not gameservers.com's fault. Valve/Steam are the only ones who can fix it.
Best things to do is wait patiently until they get it fixed. Their forums are loaded with complaints and you can see for yourself here.
http://forums.steampowered.com/forums/forumdisplay.php?f=130
Quote: September 29, 2009 - Left 4 Dead Update Released
Updates to Left 4 Dead have been released. The updates will be applied automatically when your Steam client is restarted. The major changes include:
Left 4 Dead
Made the variable "mp_gamemode" available again. Note that you can also load maps directly with different game modes by specifying it in the map command. For example, "map l4d_garage01_alleys versus" will set mp_gamemode versus for you automatically and load the first map of Crash Course
Added "mm_dedicated_force_servers" to allow specification of a list of dedicated server addresses manually used for searching (ms_force_dedicated_server is depreciated)
Updated shared libraries and DLLs preventing dedicated servers listing correctly, appearing on Steam groups, and being found via sv_search_key
Quote: September 30, 2009 - Left 4 Dead Update Released
Updates to Left 4 Dead have been released. The updates will be applied automatically when your Steam client is restarted. The major changes include:
Left 4 Dead (PC)
Item density calculation corrected for Versus games
Fixed weapon density in Crash Course
mp_gamemode now a valid command
New localized audio for Crash Course now available
Fixed achievement issues in Crash Course
Fixed dedicated servers not updating correctly to master server
Increased the timeout to fallback to listen server when searching for a dedicated server to 45 seconds
Left 4 Dead (360 dedicated only)
Item density calculation corrected for Versus games
Fixed weapon density in Crash Course
Player controlled special Infected will no longer be trapped if they spawn in rescue closets
Weapons and health kits in cabinets are now correctly respawned in the second Versus round
Fixed a deploment issue on Xbox 360 dedicated servers that resulted in collisions not being properly detected. This issue is a server only issue
I know it's annoying. I'm sure they'll fix it once enough people complain, like always...