Mr Nutt – how much do you run?
Inov8s are quite brutal. I got used to my Mudclaws fairly quickly but they still blistered my heels and killed my calves. The Roclites I just sent back (got Salomon Speedcross 2s instead) just destroyed my calves with no appearance of getting better – I was literally hobbling after every run, even short ones. They are very light though and grip extremely well.
Try the Speedcross 2s if you can – like Inov8s (and lighter) but with a wee bit of padding and heel support.
I run a fair bit and race quite often too so I'd say if my calves were suffering, many others would too.
Finbar -LOL! I meant their more "normal" shoes!