Error starting framework core

Hello,

i tried to install plexmediaserver on a ubuntu server 12 system. When i start the server i get the following errors:

Error starting framework core for /var/lib/plexmediaserver/Library/Application Support/Plex Media Server/Plug-ins/PlexThemeMusic.bundle.
Error starting framework core for /var/lib/plexmediaserver/Library/Application Support/Plex Media Server/Plug-ins/OpenSubtitles.bundle.
Error starting framework core for /var/lib/plexmediaserver/Library/Application Support/Plex Media Server/Plug-ins/The-Movie-Database.bundle.

And i cannot add a library over the webinterface.

Can anybody tell me what is wrong?