Youtube app will only default to 4/3 if you disable 720p or 1080 modes.
Re-enable >720p or the app will remain 480p 4/3 mode.
When the PS3 crashes It can erase the Display setting during restart...
Moving to a SDTV will also force 4/3 mode on the PS3 youtube companion app.
Still working here in 16/9 HD... no changes since the HD video in sig below...
SIEE PS3/PS4 Beta Tester
From SIE blog firmware 4.50 post "There is no guarantee that all USB storage devices are compatible with your system."