How can i stop clicks?

Hi,

I've just bought a v-studio 20 and installed all of the bits from the CD rom, however I am getting lots of clicking and crackling in my earphones when recording or listening to play back.  I have tried what it says it the handbook about lowering my screen resolution and changing the settings in the audio options - has anyone else had this problem or got any advice as it's driving me mad!

Cheers