Weird Waveforms

I am not sure if they are linked but I installed the latest version of Sonar (early access May) but now when ever I move the mouse over a clip a grey wave form draws over the top of the existing one and I cannot work out why this is happening. I cannot eve work out what the waveform is from, at first I thought it might be from a take lane but I opened up the lanes and saw that the part I was editing (I was editing drums fills on toms) there were no other takes in that section.
 Any idea what this might be as it is slightly annoying, as I was trying to mute sections where the toms were not playing and then when I did mute the section the orginal, say red waveform, would not then grey out when muted.