Is your big toe rubbing/ banging against the top of the shoe at the front??
I had a similar problem with some trail shoes I brought last winter. Although the grip was fine, I found that my big toe was always sore at the top. I knew they were the right length shoe, as I could get my thumb between the big toe and the end of the shoe.
What appeared to be the prob was that the front of the shoe wasnt "tall" enough, and it meant that my toe was banging against the top of the shoe.
Unfortunately by the time I had sussed this, they had been through puddles, mud etc and smelt like a sheeps backside. (well not quite, but you know what I mean).
I was therefore forced to take extreme action, and cut a hole in the shoe over the top of the toe.
I wouldnt really recomend this for lovely expensive shoes, but mine were a cheap pair of trails. It did sort the toe prob out, but I cant run in them in the rain anymore.
Obviously you may not want to do that, but it may give you an idea of what your prob is??