Help - New Paradign Signature speakers buzzing

I have new Paradigm Signature S-2s that I am using as fronts for a month or two, and have recently noticed an intermittent buzzing from one of the tweeters.

The buzz is most noticeable when I'm playing CDs with unaccompanied piano, occurring perhaps once of twice a minute, the buzzing lasting three of four second and loud enough for me to hear from 15 feet away. If I get close to the speaker, the buzzing sound appears to be clearing coming from the tweeter, which is a 1 inch gold-anodized pure-aluminum dome. There is no visible damage to the exterior of the tweeter. The buzz is heard whether I have the grilles on or off.

I also noticed when I place my ear closer to the speaker that neither tweeter (the one with the buzz or the other one) appears to be producing much if any sound, even when the pianist plays in the upper octaves.

I tried re-attaching the speaker wires(the speakers are biwired with spades - and yes, the jumpers were removes as they should be) and that seemed to result in sound to the tweeter that had been buzzing, but the intermittent buzzing continued.

The speakers are powered by an Anthem MVA-50 which is a couple of years old and the low end is sent to a Velodyne DD-15 sub. I play mostly jazz and classical and not at volumes that should stress the speakers, espcially not with the Anthem.

Before I phone Paradigm, I'd greatly appreciate any insight Audiogon posters may have either to diagnose the problem or troubleshoot it. Thanks.
- Jon