I use guiminer, i find it to be much simpler. Have you compared your speeds and settings with the wikis?
i was using guiminer and one day find out that i could get better rate with bfgminer or cgminer and it was true, i was also getting 50M/hash with the old card and when i try bfgminer i got 80.
And on the wikis people got 182 - 213M/hash with the card i got with lower speed, but there was not really any setting exept the miner wich is poclbm
uninstall old driver using proper program as ''driver fusion'' than install the new one.
thanks for the tip will try in few minutes