I
ve also noticed internet explorer can cause a half hash rate, whenever I watch a you tube video and exit abrutptly itseems to still stay resident and use half your GPU even if iexplorer isnt running
The most recent browsers are all including gpu acceleration and flash is as well your cpu is offloading video decode to the gpu. If you try it with some other modern browsers FF and Chrome and it does the same thing it's an issue with that revision of flash and your current ati drivers if not then it's between flash and ie or flash and the ati drivers.