I just bought two of the MSI 580 Gaming X and one plus version. 

On the non-plus - stock they ran about 22mhs.  I modded and got 25mhs. 

For some reason ANY modification to the memory clock COMPLETELY DESTROYS mhs.  At 2000 I get 25 mhs, bump to 2050 and it falls to 18mhs.  Slowly ramping up I might get up to 20 mhs until 2100+ will crash the card. 

I have no idea wtf is wrong.  I tried both MSI afterburner and wattman.  I tried oc the memory with no other adjustments and as soon as I touch the memory clock, mhs falls like a rock.  This happened with stock and modded bios. 

If anyone has any ideas, please give me one.  Oh - and I have hynix memory

I haven't tried modding the plus version yet.  It runs 24.5mhs stock, but temps are insane.  Like 85c already.