Firstly, why not just use CGMiner?
Also, if your card dies at a certain unstable intensity/overclock it will often restart with secondary lower clock speeds and you will get almost nothing out of it. My 7870s drop to around 25-40mhash from 460mhash when this happens. Restart your computer.
restarting the pc fixed it. I had the gpu overclocked when i first set up the pc, but when i started mining the screen froze in under a minute. The problem i wrote about happend when the gpu was running at default speeds. I guess i'll underclock the gpu a bit. i'm not even sure it's worth trying to use this old piece of shit pc. (it's been collecting dust in a corner for almost 2 years, i just though i'd set it up to have a, slow, constant mining operation going.)