For the machines not reporting, try running the below as a batch file on each of them:
reg delete HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\WindowsUpdate /v AccountDomainSid /f
reg delete HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\WindowsUpdate /v PingID /f
reg delete HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\WindowsUpdate /v SusClientId /f
net stop wuauserv
net start wuauserv
wuauclt /resetauthorization /detectnow
I've occasionally run into this problem with imaged machines and the above should resolve it.
For non-domain PCs, export the following reg keys from a domained machine and import them to the off-domain systems:
HKEY_LOCAL_MACHINE\SOFTWARE\Policies\Microsoft\Windows\WindowsUpdate
HKEY_LOCAL_MACHINE\SOFTWARE\Policies\Microsoft\Windows\WindowsUpdate\AU
That should take care of it.
Endaar