I just finished going through about a dozen abandoned cache directories that the Janitor Scan identified and told NB to remove them all. (Tediously, one at a time. It would be better if when I clicked on the message for one of them, they could all be listed in a single "Janitor Scan" dialog so I could select them all and wipe them out in one go.)
However, I then ran into another issue that got me to quit NB and restart it. When I restarted NB the Janitor Scan found all the same abandoned cache folders! The removal failed for every one. The directories appear to be untouched. Nothing relevant shows in messages.log It doesn't appear to be permissions related, as the directories can be deleted or put in the recycle bin without any need to get extra permissions. Regards, Scott