With 3 calls reported on this site within the last few hours, it has to be one of those computer-generated nuisance calls we hate. I didn't bother wasting more time by answering or calling back to identify them.
I just got one, too, on my cell phone. Left no message. I am on the Do-Not-Call list, but I am still getting 1-2 calls from people I do not know every night.