Commented Unassigned: Invoke-Expression : The variable '$OS' cannot be retrieved because it has not been set. [25500]

notebook lenovo idealpad Y470
Windows 8.1

command
.\PAL.ps1 -Log SamplePerfmonLog.blg -ThresholdFile QuickSystemOverview.xml -NumberOfProcessors 1 -TotalMemory 1 -SixyFourBit $False -AllCounterStats $False

error
[Started] Memory Pool Non-Paged Bytes
Counter data for ""...Done
Generating Charts.WARNING: Please post errors or problems with this tool to the PAL web site located at http://www.codeplex.com/PAL with the following error message and a brief description of what you were trying to do. Thank you.
Invoke-Expression : The variable '$OS' cannot be retrieved because it has not been set.
At C:\Program Files\PAL\PAL\PAL.ps1:3401 char:5
+ Invoke-Expression -Command $sCode
+ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+ CategoryInfo : InvalidOperation: (OS:String) [Invoke-Expression], RuntimeException
+ FullyQualifiedErrorId : VariableIsUndefined,Microsoft.PowerShell.Commands.InvokeExpressionCommand

PS C:\Program Files\PAL\PAL>
Comments: ** Comment from web user: raymegal **

I get the same error when running this:

PAL.ps1 -Log "Logfile.csv" -ThresholdFile .\SQLServer2008R2.xml -NumberOfProcessors 24 -TotalMemory 96 -SixtyFourBit $True

See attached screenshot.

I'm running this on a Win8.1 64-bit box.

Thanks!

PS This is a great tool.