Playback problems - echo and sound fading in & out

I have just loaded cubase AI 8.

I have 2 problems when I play back through my headphones;

  1. I get an echo on track 1
  2. on track 2, the sound starts OK, then fades in and out every 5 seconds or so.

I don’t have these problems in the “sample editor” (simply click on the track), so I know all my drivers and bus configurations are OK. Or are they ?.

Please help !.

Thanks

Peter (Scotland)