I have a very old oven, yet I can cook anything except baked potatoes. I have been able to cook them in ovens at previous apartments. Pre-heat oven, stab potatoes with fork, put potatoes in oven, leave them until done (should be about 30 minutes). I leave them in for an hour or more and they're still barely tender. Even if I have other things in the oven (like chicken) they'll cook, but the potatoes won't. Any thoughts?