1/ Over collapsing of the arch because boots are being overtightened.
2/ If it is a sharp shooting pain near the heel you may have a Plantar Fascia tendon injury.
3/ You have flat feet.
1/ Just do your boots up tight enough.
SKI BOOTS: You really should not do the front two buckles up too tight. All they really do is clamp down on the foot and cause pain.
SNOWBOARD BOOTS: Do not overtighten that binding ankle strap. SHL™ could help here if infact you are getting heel lift and over tightening to compensate.
2/ Plantar Fasciitis requires that you rest the injured area.
3/ If your feet are really flat and you have little arch shape you may really need to see a podiatrist. Preferably one who specialises in fitting ski boots.