I've just downloaded and installed the RC (900) and will give it try and let you know. The locked and inaccessible folder just happened again. The folder contained a TV episode I watched through Plex and then deleted through Plex, leaving the folder empty. The folder then became locked, with a no privilege error when I tried to open it. I took a look at open files on the system, and the CrashPlan backup service had the DrivePool letter open plus the folder on all the individual drives that are part of the pool. I restarted the CrashPlan service and the folder became accessible.
This DrivePool folder is one of the ones automatically backed up by CrashPlan. I don't know if it was being backed up at the time the file in it was deleted through Plex, but I'm not sure why CrashPlan would open an empty folder.