random call early in the morning. when we called back, it said the number is not in service

Definitely not a collection agency because I don't owe money. 3 Calls received from that number over the weekend and I sent them all to VM but no message was left.

Long distance carrier that patches calls through.  Not a spammer, or a collection agency (necessarily).  It is a 'skype' type internet assisted number though.

I received a call from this number Jan. 27, 2010. Same result: I answered it and there was nothing on the line.

When people use online services to such as Skype to make phone calls, the call goes through local telephone line in the recipient's area.  This is the number for one of the lines that Skype uses.  Thus different companies (especially if they were calling from abroad and didn't want to pay the long distance fee) or individual people all go through the same phone number.