Very Strange thing happened.

I switch from microcoinminer.exe to Cgminer.exe 3.7.2 to mine worldcoin, and my first 280X card slow to 500kh/s

I have 2 pc with four 280x cards in each. Both pc's first card slow down. Other 3 cards in both pc remain 750k. (no overheating issue, no HW error)

I did reboot, reinstall 13.12 driver, reinstall cgminer, reinstall cgwatcher. nothing helped.

It seems that microcoinminer has changed some settings in my system and it affect cgminer.

any help?