Problem with scrypt mining after sha3 mining.

[cdn1371]

I don't know is it correct place to describe my problem but i don't know where i should do it...

So let's proceed to my problem. On the begginig of my mining career i was minning coins on scrypt algorithm. Few days ago i've started mining maxcoins and today i wanted back to scrypt-mining, but when i did it i noticed that i have lower efficiency in my rig. For example i had 740 kh/s on scrypt, ~320 MH/s on SHA3 and now i have 600 kh/s on scrypt. I have 2 diffrent cgminer's for this. What's going on? i don't want to reinstall system...