Recock the bolt and dry fire it. The pressure of the powder igniting drives the center of the primer backwards. Recocking the the bolt and dry firing drives the primer center back into the casing so it can be removed. I have the same issue when using Winchester primers. When I tried Remington Kleenbores, I couldn't even open the bolt without reefing it as hard as I could. To eliminate your problem, you could try this:
http://www.prbullet.com/s-breech.htm