Dirk,

A dedicated Capture card like the ones you get with Premiere have special chips on them so that when you add an effect or transition it uses the hardware to preview and render. If you plug in an generic capture card i.e. the Studio DV card you don't get the chips and the realtime plugins for Premiere, and everything will have to be rendered. You will still be able to capture DV and preview this way but will be unable to preview any transitions or effects you apply to the edit.

Hope this helps,

Ed Smith