Sorry for late answer. Same behaviour on Guest Session (MP3 plays but seekbar remains disabled and Time is always unknown for ALL MP3, Ogg play OK).
Also on my regular user account, since I have played some Ogg, I can no longer play MP3. Each time I click an MP3, Rhythmbox hangs, must "Force Quit". No pb with the MP3 file, VLC plays it OK.
Sorry for late answer. Same behaviour on Guest Session (MP3 plays but seekbar remains disabled and Time is always unknown for ALL MP3, Ogg play OK).
Also on my regular user account, since I have played some Ogg, I can no longer play MP3. Each time I click an MP3, Rhythmbox hangs, must "Force Quit". No pb with the MP3 file, VLC plays it OK.