My issue is weird. I'm not moving around in my boots a lot, and the boots aren't too short. It's more like the toenails are rubbing on the top of the toe box of the boot. I've had it happen on innumerable pairs of shoes. The boots I've got now (Lowas) are better than my last set (Dunhams), but still having the problem.
Thinner insoles, or insoles with the front part trimmed off, to give your toes more vertical space? If your boots are leather, maybe you could get the toe box stretched out some, vertically?
Jeff