My gmail pass was different, and I have changed it.
this is a reminder to me to go around to all the sites and change the pw.
Same thing happened to me. I had a different PW from the PW that was on my MtGox site but I got that notification from Gmail. Maybe that was a notifications that people were trying to brute force it or test it against the ones they'd cracked in that list or something? This is just a total guess but I definitely had the same situ that you had.
According to what I read in #bitcoin-dev, someone from the community who's working at Google got hold of the dump and flagged all the gmail addresses he could find as possibly compromised for safety reasons. So while this is probably nothing to worry about if you didn't use your Mt. Gox password anywhere else, you should immediately change it if you did.
Bravo to gmail if that is the case. Luckily I use different passwords for everything important and several different ones for things unimportant. However, I was still greeted with a 'change your password due to suspicious activity' when logging into gmail.