ztipowershell non-zero return code

hi all.

Running MDT2012 and have setup a 'Run Powershell' Task. This seems to run some Microsoft.BDD.TaskSequncePSHost.exe process but its returning an error and not running:

ZTI ERROR - Non-zero return code by ZTIPowershell, rc = -532459699 0xE0434F4D

I've tested a simple PS script that simply says write-host "testing' and get the same error. Any ideas?