Just a quick update. AJ Braman at MusicMan has been amazingly helpful and great about keeping in touch with me and the EBay buyer. I've been in an e-mail chain with both of them for a couple days. The problem could not be diagnosed over e-mail but the EBay buyer agreed (after I called EBay and made sure he was still covered by their Buyer Protection) to ship the bass to MusicMan in SLO, CA and at that point I'll refund him.
Thanks to all you guys for chiming in; sorry to post in the forum. And props to Sterling and all the good people at MM for great instruments backed by great customer service. Even the best products occasionally have problems; it's how you tackle them that matters!