MWPdx

So every time I have the chain on the largest chainring in the front, and I push hard at all on the pedals, it violently jumps off the chainring to the outside (right). As far as I can tell it doesn't matter what gear it's in on the cassette, it's done it on the smallest ring and the mid-large rings. I'm also pretty sure that the frond derailleur is adjusted properly as it shifts just fine between all gears in the front. I've had the bike (specialized allez) for probably 4-5 years and it's never done anything like this before. It seems to have a habit of doing it at the worst possible times, leaving me immobilized in the middle of busy intersections/etc.