I have selected various Beat loops and sequenced them in the AD midi track.
When I muted one of these loops, I noticed that AD was still playing and discovered that the orange arrow was lit in the properties window and AD was playing the Beat currently selected in that window - as well as the loop in the midi track... chaos.
I can switch it off and it's OK for that take but it switches itself on again next time round. Most annoying.
iDrums does this too but has a Slave to Host button that switches it to playing only the content of the loops in the midi track but I cannot find how to configure this in AD.
Anyone any ideas?

On the "Beats" tab of AD (in the upper right hand corner) there is a "Sync" button beneath "Host" that links the play button inside AD to the transport of SONAR. Disable that button and see if you still have issues (orange is on/dark grey is off).

Thanks, mettelus, that's the answer.
I originally set the Sync thinking it would have the effect I have been missing but clearly I got the wrong end of the stick.