In reply to goose299:
I think I've had it - only a podiatrist seemed willing to give it a name, and physios I talked to about it hadn't heard of metatarsalgia. In my case, it took quite a while - a few weeks - to sort itself out. It came on about 3 miles into a half-marathon, and was very painful to walk on for some time afterwards.
To prevent a recurrence, I've been using orthotic insoles and have made a point of making sure my shoes are a roomy fit across the forefoot. This does cause a few problems with finding suitable shoes, since I have quite wide feet. However, it's been working, since I haven't had a problem since.
If it's really sore at the moment, I doubt it'll be in decent shape for a run on Christmas Day - sorry.