Perhaps this will help somebody. I don't know.

Immediately after upgrading our Primary Servers to 11.1, our Windows 7 (64-bit) workstations began exhibiting the following symptoms:
- "The local computer username or password is not valid" upon login (we use DLU)
- "Fatal: Location Aware Enforcer Event Queue had an unhandled exception" in the ZESEventLog.
- Closest Server Rools are empty.

I sensed that to fix the problem, we needed to upgrade our Clients to 11.1. But it was a Catch-22 -- they were no longer communicating with our Primary Servers. So they weren't picking up the System Update.

In our environment, we really couldn't uninstall the ZCM 11.0 Agent, and install the ZCM 11.1 Agent, on every computer.

Our workaround was to run the ZESM Agent installer (setup.exe) for 11.1, and then after that, they were at least able to connect to our Primary Servers and update to 11.1 the rest of the way through System Update.