Black Lab, round 2

Took Roxie to the vet today for a check-up. Fortunately, there weren't any other critters in the waiting room when we got there. But as we came out of the exam room, this black lab came lumbering up to us and then everybody lunged (Roxie launched off my foot and i have a very nice scratch) BL's owner and the receptionist finally show up and BL's owner says, "Oh hey, I think I saw you at the lake this weekend" um, yeah and you're still not controlling your dog. I didn't really get a chance to say anything to him because I figured getting Roxie out of sight was more important. I don't know if it's something she does or what that sets other dogs off, but I'm hoping the training class helps.