Unable to run the Get-ManagementRoleAssignment cmdlet in MSE 2007 SP1

Hi,

I am trying to run the Get-ManagementRoleAssignment cmdlet in MSE 2007 SP1 and get the returned response
 
"The term "Get-managementroleAssignment" is not recognized as a cmdlet, function, operable program or script file. Verify the term and try again."

This is apparently caused by not being a member of "Microsoft Exchange Security Groups -> Exchange Organization Administrators" but my account is part of this group.

Is there anything I have missed or am missing in order to get this cmdlet to run?

Thanks in advance

Peter