I must be missing something obvious here.
We have a GPO linked to a computer OU.
The GPO runs a VB logon script (a user policy) when users log on.
I was just about to enable loopback processing on this GPO to allow it to take effect, but I realized that it was already being applied to all users who log on to the PCs in the computer OU in question.
None of the GPOs in AD currently have loopback processing enabled (I checked all of them).
Does anyone know what might be going on here?