Whenever opening more than 3 or 4 Youtube videos (or any flash players, for that matter), my system would crash with the error above.
Fortunately, it seems that AMD finally got around to fixing this in the 14.9 Catalyst suite. I've tested it by opening about twenty movies, which makes it sound like you are in a crowded market or something :).
You can grab the latest Windows 7 / 8.1 x64 drivers here: AMD Driver Download
My graphics card: Sapphire R9 290X Tri-X.