Cannot validate argument on parameter

Hi all,

I try to run a poweshell script from a policy rule, but get an error in the EDM Server log. Are there any one who can explain why this happens?

This is the beginning of the script:

function onPostModify($Request) {    $displayName = [string]$Request.Get('displayName')    $alias       = [string]$Request.Get('sAMAccountName')    # Same error > $alias       = $Request.Get('sAMAccountName')

...
}

Error:

Log Name:      EDM Server

Source:        EDM

Date:          03.08.2011 14:46:58

Event ID:      2000

Task Category: Policy

Level:         Error

Keywords:      Classic

User:         <removed>

Computer:      <removed>

Description:

Post-processing operation on object caused a policy violation.

Policy: Runs the script '<removed>'

Object: CN=Benjamin Test,OU=Users,DC=one,DC=two

Details: The 'Script Execution' policy encountered an error when running the script '<removed>'. Cannot validate argument on parameter 'Alias'. The argument is null or empty. Supply an argument that is not null or empty and then try the command again.

Event Xml:

<Event xmlns="http://schemas.microsoft.com/win/2004/08/events/event">

  <System>

    <Provider Name="EDM" />

    <EventID Qualifiers="49152">2000</EventID>

    <Level>2</Level>

    <Task>2</Task>

    <Keywords>0x80000000000000</Keywords>

    <TimeCreated SystemTime="2011-08-03T12:46:58.000Z" />

    <EventRecordID>314508</EventRecordID>

    <Channel>EDM Server</Channel>

    <Computer><removed></Computer>

    <Security UserID="<removed>" />

  </System>

  <EventData>

    <Data>Runs the script '<removed>'</Data>

    <Data>CN=Benjamin Test,OU=Users,DC=one,DC=two</Data>

    <Data>The 'Script Execution' policy encountered an error when running the script '<removed>'. Cannot validate argument on parameter 'Alias'. The argument is null or empty. Supply an argument that is not null or empty and then try the command again.</Data>

  </EventData>

</Event>