Most of the views here are from trolling bots...which are automated scanners for keywords for search engines.

Our PN forum is rather slow on weekends, and always has been.

Here is a very complete website to help you with foot pain and foot issues:

http://www.northcoastfootcare.com/

People can have stress fractures in the arch(metatarsals), mostly from poor bone density. They can happen at any age. The arch may "fall" also with age. And there is a condition called Charcot's Foot, which accompanies poor glucose utilization. Charcot's Foot, has serious swelling with it, and so does a broken bone.
http://www.google.com/imgres?imgurl=...9QEwAQ&dur=365
Charcot's foot is a serious thing and can lead to foot ulcers.
You can also have gout in the foot, from uric acid which is the main type, but there is also pseudogout, which is more common in women and involves calcium.
http://www.mayoclinic.com/health/pseudogout/DS00717
And Echoes is correct about fasciitis.
The nerves in the instep can become compressed from pressure from the tarsal ligament. The Northcoast link has good anatomy diagrams to show nerve distributions in the foot.

I think you should see a good podiatrist ASAP.
PN itself is often a secondary manifestation of a mechanical foot problem, of which there are many.