I've had this message a couple of times today from Origin, even though I've been logged in on my rig all morning. As a precaution I've changed my security settings and password, although I'm not sure if anybody else did manage to get access to my account or not. Anybody ever seen this?
Funnily enough I got the same message yesterday,but I was logged in with my other computer at the time,so unless you have another computer you could have been logged into at the time I think you did the right thing changing your security details.
I've just had it again after changing my details. I'm certainly not logged in elsewhere either so it's pretty strange and I'm pretty sure nobody would have hacked my new password that quickly. I'll have a root around the EA forums.
The fact it did it after you'd just changed your login etc does rather smack of an EA style bug rather than hacking...unless someone reeeeaaaallly wanted your copy of Leisure Suite Larry...
I've had the odd bug with Origin recently. Last night I couldn't click on any games in the store, said that the pages didn't exist. They seem to work now, though.