As reported in another thread - to which I couldn't add - 10.2 does not always work. I could not play videos from YouTube - sound OK, no image - but could play videos from Vimeo. Internet explorer was fine everywhere.
I Uninstalled it and re-installed a few times without success. I finally installed 10.1 and everything is back to normal.
I have a laptop, a Lenovo IdeaPad Y730 (P8400, 4gig). It has a ATI Mobility Radeon HD 3650 (Lenovo) video card.