Are you running these is your server.cfg ?
// readyup plugin commands
l4d_ready_enabled 1
l4d_ready_both_halves 0
l4d_ready_minimum_players 5
l4d_ready_search_key_disable 0
If so take them out , It looks like the server cfg is exec the cvar instead of the ugc cfg.
In your post you have Source Mod Ver is 1.7.1
That is your meta mod version
While in game type in console sm version
And look for something that looks like this,
SourceMod Version Information:
SourceMod Version: 1.2.4-de
SourcePawn Engine: SourcePawn 1.1, jit-x86 (build 1.2.4-dev)
SourcePawn API: v1 = 4, v2 = 3
Compiled on: Oct 1 2009 05:59:28
Build ID: 2790:716ad2a236fe-dev
http://www.sourcemod.net/
Copy and paste what you have.
Thanks
Snowy