MIDI Notes Sustaining/feeding back?

Every now and then I have a problem whereby MIDI notes (can be single bass notes or keyboard chords) play in Sonar and go into what sounds like a feedback loop, although the feedback doesn't compound on itself, it's just as if they start to sustain forever. I can only cure this by saving and closing Sonar, then reopening.  I get it with MIDI playing through both soft synths and external hardware synths. I've had it for at least a couple of years but it only crops up every couple of months or so, with no special circumstances so I can't report it.
 
Does anyone else suffer from this?  I remember some thread(s) a long time ago about MIDI bleed or leak across channels, so I don't know it this is still a buried bug somewhere.