This appears to use more memory. My LTC mining 7950s drop about 10-15% when I mine MMC on the same machine.
Just reduce mining threads.
On a 4 core cpu - 2 MMC mining threads, not drop in GPU Hashrate
4 mining threads -> hashrate drops 20%!
You can easily mine MMC without affecting scrypt mining performance. Just don't use all threads.
I try it yesterday. Still same. I think its possible for i have any problem in my computer. But anyone's know what is. Finally say to me, can it be the motherboard, but i don't want lose more time/money on parts just for max 100 khs. When start failing more, maybe i try to change it. But first say to me, its the ram or the HHDs, i make all the tests all correct. Second say to me, the PSU. Still same. Sent to me new AMD 7870 same problems same hashrate and finally say to me, maybe the motherboard.
The other problem its only with Windows 2008 server the monitor turn on. With another windows, some times it boot correctly some times say "bad resolution"... Don't try with Linux.
@1.68 HPM and difficulty is flying up 
That isn’t luck 