EDIT: Forget my suggestion, i just realised that i missed the part where you tell you have allready tried the executionpolicy
It sounds like the Execution Policy on the machine is perventing it from running.
You are try to set it manually on the machine by opening a administrative powershell and write; Set-Executionpolicy ByPass
We do set it via the client settings in SCCM 2012, in the "Computer agent" section, there is a "powershell execution policy" option.