GtW,
Although the message was spam-y looking, it was a bit more sinister than that, methinks. It actually rolled up following the loading of a trojan based rogue antispyware application. This particular one is doing the rounds now and a lot of folk are having trouble removing it.
Who knows what info the trojans send home? Email addy? Possibly. If it has full access to the system for the time it's on, you wouldn't be sure- or I wouldn't - that an address hadn't been harvested.
So I think a reasonable amount of paranoia is called for, in case it isn't a coincidence.