My guess... No WMI or broken WMI on the remote system or the system is not available period. That is why I said above you should also add some more to the code for a production run.

Try adding the PING UDF and this ConfirmWMI UDF to the code or at least testint the WMI with this code on the one that breaks.

Also, what version of KiXtart are you using?
 
Function ConfirmWMI(optional $sComputer)
  Dim $objWMIService,$objWMISetting,$colWMISettings
  $sComputer=IIf(Not $sComputer,'','\\'+Join(Split($sComputer,'\'),'',3)+'\')
  $objWMIService  = GetObject("winmgmts:{impersonationLevel=impersonate}!"+$sComputer+'root\cimv2')
  If @ERROR
    $ConfirmWMI = Val("&"+Right(DecToHex(@ERROR),4))
    Exit $ConfirmWMI
  EndIf
  $colWMISettings = $objWMIService.ExecQuery("Select * from Win32_WMISetting")
  For Each $objWMISetting In $colWMISettings
    $ConfirmWMI = $objWMISetting.BuildVersion
  Next
  Exit $ConfirmWMI
EndFunction