When I first configured the 'Prefetch directory users' (under Definitions & Users, Authentication Servers, Advanced) I selected the pre-configured AD server then AD groups I want to be prefetched.
I then clicked on 'Open Prefetch live log' - log viewing page opened
I clicked on 'Prefetch now'
Open log window remained empty
Closed Window
Went into Logging & Reporting - checked log, it was populated
Went back into the Authentication Servers / Advanced page again, ran same prefetch process, open log was populated in window.
Deleted pre-fetch settings and tried to recreate same situation but couldn't replicate.
Will try again on a fresh install - has anyone else seen this?