How this happened is a complete mystery. Apparently someone started sending spam from it last night at 2:30 AM. McAfee was running with a Firewall, and says nothing is wrong. System Mechanics says the same. I had a secure password, too, which I promptly changed. We do use a wireless modem, but it should be secure. At first I thought it was my Android phone, but that doesn't fit the timing. I wasn't using my phone at 2:30 AM.
Anyway, I'm extremely sorry if you received spam from my account.