Several calls from this number with "Unknown Name" in ID.
Suspect it's political (with elections coming up in a few weeks) but that's just a hunch at this point.

One other reference found on the web: http://www.whycall.me/617-778-7321.html
That commenter tried to call back to ask for the calls to stop (implying he'd received more than one) and was hung up on. This may be because the number was spoofed (and the real owner of 617-778-7321 is fed up with strangers asking him to stop calling!) or because it's the actual caller and he's up to no good.

Something stinks, either way.

I just received a similar call from a number just one digit different, 617-778-7322 (http://800notes.com/Phone.aspx/1-617-778-7322) Coincidence? Probably not.

I've been getting many calls from 617-778-7321 and variants e.g, *7322, *7323, *7324, etc.  Caller ID is shown as M R & ASSOCIATE.  I've answered them twice (thinking it might be a real company).  The first time, a man's voice said "hello", but when I asked who he was he would not answer.  The next time I answered, I said "hello" several times but no one responded.  This is likely someone trolling for real numbers to sell to telemarketers.  Now, when I see this caller ID, I pick up and then hang up immediately.  I wish I could block it.  
NOTE: I reported the problem to my land line provider (Comcast), but I don't know if they're really do anything about it.

got a call from this number on my cell. I answered "hello" and there was a small delay before I heard a woman's voice on the other end, with telemarketing-like sounds in the background.