Cannot invoke an external PowerCLI script with Orchestrator

I am using the default "Invoke an External Script" vCO workflow provided by the PowerShell plug-in.

I have set up my powershell server on the same Windows Server as vCO is installed in.  I am able to run a simple PowerCLI script if I use the default "Invoke a PowerShell Script" workflow and it runs fine as the script is located internally to vCO.

However, now I'm attempting to call a simple PowerCLI script located external to vCO at c:\report.ps1 on the PowerShell server using the "Invoke an External Script" workflow.

When I try to do it this way, the workflow fails with the following output under "Logs":

[2014-01-28 19:42:32.447] [D] Invoke command in session 261371cc-3b28-45e3-bf6b-df7bddeeb2c9

[2014-01-28 19:42:33.181] [I] PowerShellInvocationError: Errors found while executing script

System.Management.Automation.RuntimeException: The expression after '&' in a pipeline element produced an invalid object. It must result in a command name, script block or CommandInfo object.

   at System.Management.Automation.CommandNode.CreateCommandProcessor(Int32& index, ExecutionContext context)

   at System.Management.Automation.CommandNode.AddToPipeline(PipelineProcessor pipeline, ExecutionContext context)

   at System.Management.Automation.PipelineNode.Execute(Array input, Pipe outputPipe, ArrayList& resultList, ExecutionContext context)

   at System.Management.Automation.StatementListNode.ExecuteStatement(ParseTreeNode statement, Array input, Pipe outputPipe, ArrayList& resultList, ExecutionContext context)

(Dynamic Script Module name : invokeScript#14)

Any ideas?

Thanks!