I imported a party from a Game Save from older BGII (single player), and each had Speed Boots on. Only certain characters work, generally the back line party members, but any other equipped with the same gear won't. I tried importing other saves, and it also happened with them. In addition, any Haste or Improved Haste spells/potions have no effect.
All other specialty boots work as they should, only the Speed Boots will not.