QB 2.x never had any issues when it came to running "util.cleanDir" on our nightly builds to wipe the workspaces clean. Since switching to QB 3.x it seems to be failing at least once a night across the different configurations. One of the folders that threw the exception was checked out the day before but never has anything access from it (as it's part of an art tool-chain not used when building code) so shouldn't have had anything locking that folder (it's possible a virus scanner or windows could have been doing something at exactly the wrong moment in that folder).

This is really serious for us as the cleanDir running partially leaves that agent in an unknown state where Perforce can think a lot of files exist on the hard-drive that have subsequently been manually deleted (so it won't grab them again).