Exception calling "Find"

I have a script that does a nice check to see if two groups belong to admins group on each server.

It kind of works apart from , if there is a server is the list that in no longer in AD , it returns the results from the last server.

The code below will run ok , if a server is no longer in the domain the line that reads

...psbase.children.find(”Administrators”) will sometimes error with

$Result = @()
$TestResult = @()

foreach($server in (gc c:\Input\ListOfComputers.txt)){
$computer = [ADSI](”WinNT://” + $server + “,computer”)
$Group = $computer.psbase.children.find(”Administrators”)


function getAdmins
{$members = ($Group.psbase.invoke(”Members”) | %{$_.GetType().InvokeMember(”Adspath”, ‘GetProperty’, $null, $_, $null)}) -replace ('WinNT://d30.intra/' + $server + '/'), '' -replace ('WinNT://d30.intra/', 'd30.intra\') -replace ('WinNT://', '')
$members
}

$TestResult = ( getAdmins )
# Write-Host $TestResult.GetType().FullName


$Result += Write-Output "SERVER: $server"
$Result += Write-Output ' '
$Result += ( getAdmins )

if (-not ($TestResult -like '*/svc_Maneng'))
{
    $Result += '					svc_Maneng Missing'
}

if (-not ($TestResult -like '*/m_DECO_COG_DPEMEA_admins'))
{
    $Result += '					m_DECO_COG_DPEMEA_admins is Missing'
}



$Result += Write-Output '____________________________'
$Result += Write-Output ' '
}


$Result > c:\Output\output2.txt
Invoke-Item c:\Output\output2.txt