No, there weren't any incoming calls.

I checked the ring volume with Speaker 601 and it is perfectly audible.

I think I'm going to chalk this up to a glitch. We are getting ready to replace our VMS card with a flash-drive version, as our current card (hard drive version) has been giving us problems for a few weeks by randomly leaving 2-3 copies of voice mails in the voice mail boxes, and leaving ports open until all four are open and it needs to be reset.

Perhaps it's possible that this problem arose from the VM card malfunctioning, I don't know.