There is a problem with the scoreboard objectives that involve "stat.useItem.minecraft.NAME", where NAME is a weapon or a piece of armor.
If you for example add "stat.useItem.minecraft.diamond_sword" and you rightclick with a diamond sword, it doesn't add a score to you. Same with Axes, Shovels, Pickaxes, Armor, and actually everything that is not use- or placeable.

Please fix this in the next snapshot (if possible) because this bug exists for a long time now and really makes some things more difficult than they would be without this bug.