I followed the upgrade steps from http://confluence.jetbrains.net/display/TCD7/Upgrade
and, after upgrading to 7.1.1, it seems that VCS plugin are not correctly installed on agents
I've tried to solve taking inspiration from http://devnet.jetbrains.net/message/5278534#5278534
I've also reinstalled some agents from scracth but it seems not to solve too.
We have the same problem in differente agents (automatically or manually upgraded)
You can find some log from one of the agent in the attachement.
Maybe I'm doing something worng and you can help me.