Running MDT 2012 on three servers 2008 R2, two are connecting to the monitoring service of the third. When accessing to the monitoring section of the workbench for the last installed server I received the following error:
System.InvalidOperationException: An error occurred while processing this request.
at Microsoft.BDD.Workbench.Utility.RunPSCommand(String commandString, Dictionary`2 parameters)
The solution was to disable the proxy on the IE. With this, the monitoring was running fine on the workbench console for the new server.