I have _not_ experienced this problem myself, in either the standalone or plug-in (AU for Logic 8 or Live). No "phantom notes" here!
I did, however, once have _both_ the standalone and the plug-in operating at the same time, and, having not looked at my dock (and hearing the distinct sound of the vibraphone in addition to the piano, at a different tuning no less!), I was mightily confused by the "extra" noise. (Since then, the standalone icon has been removed from my dock -- I had hit it accidentally when opening up something else, and the blue just blends in a little _too_ well with my current desktop background. %^)
I believe I had done this once or twice before, and the results were always strange.
Also, I had once set some CD cases on top of the trigger pads on my Axiom 61. Indeed, as I was playing, odd, unplayed notes were being emitted from the program, and I couldn't understand why. Of course, not being one to ever really _use_ these pads, I had to wait a while until the reason finally dawned on me (by accident, I'm sure -- I must have moved the cases or some such nonsense). I'm so smart sometimes!!!
"Our developers, who art in Toulouse, hallowed be thy physical-models.
Thy version 4 come, thy new instruments be done, in the computer as it is in the wood!"