SRAM X0 T-Type

Hi,

I have had a bike with an X0 T-type Derailleur fitted from new (18 months) and it has worked flawlessly for that time. In the last day, for some reason, it does not shift into the two largest gears on the back. Each time I try to change to 2nd largest gear the jockey wheel in the cage is in contact with the chain on the cassette and it seizes. I worked fine 2 days ago, it hasn't had any knocks and changes perfectly in the first 10 gears so it is not the micro adjust. I would say it is the B-screw adjust, but there isn't one!