[2008 Server] Task Scheduler Ignoring the Task

Hi, 

I'm stuck in a weird situation,

I've planned a Task, wich launching a powershell script wich launch a backup of the server on a network share.

and it works well ! Until a week end a half, after this date, the task is not even launched or failed with an error code.

Nothing appends, as if it doesn't even exist anymore.

The task is still in the scheduler the next start is planned correctly. But nothing appens (not even a trace in the log).

A manual Start works perfectly.

After a reboot of the server the Task works great for a week and a half.

The other tasks seems to work great.

If anybody already had this issue, I'm Interested in any suggestions.

here's my Task in XML

<Task version="1.2" xmlns="http://schemas.microsoft.com/windows/2004/02/mit/task">
  <RegistrationInfo>
    <Date>2012-04-20T16:10:24.5574</Date>
    <Author>SERVEUR\abtecadmin</Author>
  </RegistrationInfo>
  <Triggers>
    <CalendarTrigger>
      <StartBoundary>2012-04-20T23:00:00</StartBoundary>
      <Enabled>true</Enabled>
      <ScheduleByWeek>
        <DaysOfWeek>
          <Monday />
          <Tuesday />
          <Wednesday />
          <Thursday />
          <Friday />
        </DaysOfWeek>
        <WeeksInterval>1</WeeksInterval>
      </ScheduleByWeek>
    </CalendarTrigger>
  </Triggers>
  <Principals>
    <Principal id="Author">
      <UserId>SERVEUR\zaservice</UserId>
      <LogonType>Password</LogonType>
      <RunLevel>HighestAvailable</RunLevel>
    </Principal>
  </Principals>
  <Settings>
    <IdleSettings>
      <Duration>PT10M</Duration>
      <WaitTimeout>PT1H</WaitTimeout>
      <StopOnIdleEnd>true</StopOnIdleEnd>
      <RestartOnIdle>false</RestartOnIdle>
    </IdleSettings>
    <MultipleInstancesPolicy>Parallel</MultipleInstancesPolicy>
    <DisallowStartIfOnBatteries>false</DisallowStartIfOnBatteries>
    <StopIfGoingOnBatteries>true</StopIfGoingOnBatteries>
    <AllowHardTerminate>true</AllowHardTerminate>
    <StartWhenAvailable>true</StartWhenAvailable>
    <RunOnlyIfNetworkAvailable>false</RunOnlyIfNetworkAvailable>
    <AllowStartOnDemand>true</AllowStartOnDemand>
    <Enabled>true</Enabled>
    <Hidden>false</Hidden>
    <RunOnlyIfIdle>false</RunOnlyIfIdle>
    <WakeToRun>false</WakeToRun>
    <ExecutionTimeLimit>P3D</ExecutionTimeLimit>
    <Priority>7</Priority>
    <RestartOnFailure>
      <Interval>PT10M</Interval>
      <Count>3</Count>
    </RestartOnFailure>
  </Settings>
  <Actions Context="Author">
    <Exec>
      <Command>C:\Windows\System32\WindowsPowerShell\v1.0\powershell.exe</Command>
      <Arguments>F:\ABTEC\scripts\Svg_Serveur.ps1</Arguments>
    </Exec>
  </Actions>
</Task>