I'm running 14.04
I've noticed recently the control buttons are missing from all Youtube videos I try to view. I can still click on and use the controls (play, full screen, etc.) but they are all invisible. Only the playback time is visible and the volume control shows on mouseover.
I've tried reinstalling the flashplugin-installer package to no effect. Right-clicking on the video gives me the html5 context menu so I suppose it's not a flash problem in the first place.
This problem is occurring in Firefox, from Chromium everything appears normally.
00:02.0 VGA compatible controller: Intel Corporation Core Processor Integrated Graphics Controller (rev 02) Subsystem: Hewlett-Packard Company Device 144c Kernel driver in use: i915 00:16.0 Communication controller: Intel Corporation 5 Series/3400 Series Chipset HECI Controller (rev 06)