i think its a sign of popularity 
probably it was triggered by logging in from an infected source…mmm viruses, say someone has that msn spyware where the messenger sends off commands at a certain time based on power users commands, even when the original user is logged off. i’ve received so many of those that i’ve ended up blocking some people due to the annoyance…and then you login from that computer…
change your password alex. that would probably be the first solution.