Right How, much ram you got?
512MB 1Gb 2GB 4GB?
And if i was you... i'll unstall everything that's related to your card... drivers etc, and reinstall DX9 and the latest drivers.
btw, have you done any overtclocking? or edited anything in the CCC? or is it at default?
also when you say memory low? is this an error msg?
can i see a screen please.