Running a task schedule as a different user

Greetings

Operating System: Windows Server 2008 R2

Server Role: Domain Controller

I'm trying to create a task to run automatically using Task scheduler which will run a Powershell script. I'm running this on a Domain Controller and will be creating the task using my Domain Admin account, now I have a service account that I wish to use to run the task as and when I change the run as to the service account I get the following error:

I can confirm the username / password combination is correct, the service account has the rights to the folder to where the powershell script is and has the correct permissions to the right group in AD for the script to successful right ok. The task schedule work fine and runs fine when using my Domain Admin account.

Any assistance would be gratefully welcome.

Regards

S