The WCF (Windows Communication Foundation) security settings were different between the client and server.
The correct this problem, the WCF security settings between the client and the server must match.
1. On the Blueprint server, go to \Program Files (x86)\PharosSystems\Blueprint\Bin (NOTE: on a 32-bit server, this would be in \Program Files\PharosSystems\Blueprint\Bin) and copy these files:
2. Paste them into the \Program Files\PharosSystems\Blueprint\bin directory on the client workstation, overwriting the duplicates.
There is no need to restart any services or processes on the client.