Make sure the cleat is in the right position.
(pic pinched from joe friel's blog - which you should read)
There is a growing body of bike-fit lore suggesting having the cleat further back than would be traditionally proposed is desirable.
Steve Hogg in cycling news makes a good point, and then there is the biomac mxc 2 shoe design. Joe Friel, who is arguably the most important cycling fitness guru on earth at present likes them.
Might be worth a try pushing the cleats a few mm back and seeing how things go...