"An error occurred while loading the catalog"

NSS 5.1.0.29, Win7x64, not using Norton online storage

 

When I browse the "Norton Backup Drive" from within Explorer, I get an error dialog, "An error occurred while loading the catalog" intermittently.  To continue to navigate, I have to navigate up a level, then back to where the error occured.  The errors occur intermittently and on various folders.  Its a pretty small backup: 25K files, 8.3GB, no large directories or anything.

 

Does anyone else have this issue or a cause/resolution?