I'm seeing this bug as well. I've seen it several times and have learned to use the backup/restore as a work-around.

The circumstance I see the bug seems to be when I take the N800 away from my home network. I browse offline for a while. When I return home, all of the feeds are gone. Maybe it has to do with the RSS reader quitting while offline?

The feeds don't disappear at home. The N800 is online and on/off/shutdown at various times. I've seen the feeds disappear 2 or 3 times now when returning home after using it away/offline.