GUI is pretty much non-responsive or non-existent. A reboot usually brings it back but it usually never refreshes completely.
It’s probably running the indexing and thumbnailing tasks, like it will after every firmware upgrade.
Rebooting will only restart these tasks.
Either leave it alone for a couple of days (if you have a lot of media) to let these tasks finish, or kill them off:
My media library appears mostly unavailable over DLNA
Have you checked in the Twonky UI to see what shares it’s now looking at for media? Firmware upgrades (and most other restarts) trash the Twonky settings. You can address this to some extent:
http://community.wd.com/t5/My-Cloud/FAQ-Twonky-DLNA-Media-Server-Setup-amp-Use/td-p/858810
ps. you shouldn’t have to know these things… the device should ‘just work’. The reality is a little different.
