If I'm not wrong, it's OpenCL AMD bug...
Disabling flash hardware acceleration fix the problem, at least for now.
If you play hardware accelerated videos, the clock of the GPU AMD / ATI is lower, 400MHz GPU / 900MHz RAM,
and then also slows down the mining.
Thank you for the reply, knowing what's wrong makes me feel a lot better

. I was afraid it was a more serious problem since its a new card. I will just avoid watching videos on the PC while mining then. Not so hard to do since I have a laptop and I can watch them there

.