I've never had an issue where it was a direct pain in my feet / foot bottom. I think it might be a boot issue, as you pointed out above.
Do you wear good socks?
I was wearing some normal socks and they might have bunched up. On the hill last year I don't remember fatigued feet so hopefully I wont need to spring for new boots.
as with anything, if it's the first time doing something in a while, you are going to use muscles that aren't normally used as much.
I'll give it a few more tries ad see.