Just curious but since you have two video cards, try pausing one of the slots and see what that does to the CPU and to the frame times of the still working GPU slot.
You won't get help from the folding forums, for two basic reasons. First all beta support is done only in the beta forums and you have to be an official beta tester to post there. If you post in the general forums, the thread will be shut down virtually immediately. Second, the AMD Linux GPU core_17 were released as unsupported software. However, if you do post in the beta forums, others can comment and offer suggestions and the thread won't be shut down.
Perhaps sacrilege but also likely the best place to get good answers for this problem is the Curecoin IRC channel. There should be lots of experienced Linux AMD/ATI folders there.