I'm a total noob

I did not toch anything, and did not know how to check that.
I can only say that on my web-ui, engine and memclock remain stable before and after the drop.
I did not know what the overdrive is (and how to check that under Linux Bamt).
And it is happening to the darkcoin kernel only?
Another interesting note about this issue is that I could mine VTC using badman's version at 500kh each for hours and then when I switch to mine Hiro without rebooting, it will still start off at 2.65 Mh per card for the first few mins and then it will drop down to 2.41 Mh. I won't be able to get 2.65 Mh again until I reboot the machine.
Something triggered the card to go into a certain state that make it drop for the rest of the current boot cycle. Is there something in the Darkcoin kernel code that put it into that state or... ?