Powershell – Listing the parameters of Get-Eventlog cmdlet

You're missing the $_ to indicate which object's msDS-UserPasswordExpiryTimeComputed attribute to use in your expression. The $_ variable is the default current object in the pipeline. You would find the value in $_."msDS-UserPasswordExpiryTimeComputed".

Get-ADUser -Filter * -Properties "msDS-UserPasswordExpiryTimeComputed" | 
  Select-Object name,samaccountname,@{Name="Expry";Expression={[datetime]::FromFileTime($_."msDS-UserPasswordExpiryTimeComputed")}}

I'm sort of thinking aloud here, but maybe this is related to this known issue with PowerShell 2.0 which has been resolved in PowerShell 3.0 CTP2. I know you don't explicitly call Add-Member, but the Select statement with a calculated field sort of accomplishes the same thing. It seems like they could be related. I ran some tests to compare PS 2.0 and 3.0 and 3.0CTP2 never once failed on your query. PowerShell 2.0 gave me different output every time.

If you can't install PS 3.0 yet, I've rewritten part of your script, but it doesn't have all of the columns that your original does. I'll let you tweak it to perfection. You'll just need to use Add-Member to add more properties.

Get-MailboxDatabase -IncludePre | foreach-object {add-member -inputobject $_ -membertype noteproperty -name mailboxdbsizeinGB -value ([math]::Round(([int64](get-wmiobject cim_datafile -computername $_.server -filter ('name=''' + $_.edbfilepath.pathname.replace("\","\\") + '''')).filesize / 1GB),2)) ; add-member -inputobject $_ -membertype noteproperty -name mailboxdbsizeinMB -value ([math]::Round(([int64](get-wmiobject cim_datafile -computername $_.server -filter ('name=''' + $_.edbfilepath.pathname.replace("\","\\") + '''')).filesize / 1MB),2)); add-member -inputobject $_ -membertype noteproperty -name numberofMailboxes -value (($_ | Get-Mailbox | Measure-Object).Count) -PassThru} | Sort-Object mailboxdbsizeinGB -Descending | format-table identity,mailboxdbsizeinGB,mailboxdbsizeinMB,numberofMailBoxes -Autosize

Keep in mind that if you install PS 3.0, you can still launch version 2.0 if you add the -version 2.0 parameter after the powershell.exe call.