Ok, start with the basics.

Do you have the latest drivers installed?

Is it the 7970 which is really causing the problems or does the mining application have - let's say- problems connection to the mining pool? Could be that the card is just patiently waiting for data.

Stil not much info to go on. General advise would be to analyze the output of the mining application and the graphics card monitoring applications. Do you see messages? Google them. Or post them here...

Tahoda