Hmmm... I'm scratching my head about this one.
Maybe it's a WiFi signal strength issue. What is your WiFi Strength (Maintenance menu)?
Maybe it's a browser issue. Try closing the browser window, clearing the cache, open a new window and enter the IP address manually (do not use a bookmark).
Maybe it's a HDD issue. View the B2's HDD as NAS, and see that the artwork files are still there and are viewable on your computer.