First off, there were numerous issues with your layout. Not least you had the stretched the size of the inv sprite, and assigned imagepoints that were not only too close to one another so that when the select sprite was over one weapon it was over another, but when it was stretched it was on a decimal X,Y position (i.e. 302.5, 272.5)
I have modified it so that the spacing is sufficient for you and that you can easily change it by altering a few numbers in the move inside inv group. I have also renamed your mono spites animations so it will allow the game to flow nicer, given the way in which animations are selected, and finally I have cleaned things up a bit, but not to a degree where the changes made will confuse you too much.
https://dl.dropboxusercontent.com/u/108 ... eapon.capx
P.S. I didnt' need to use Regex magic given what I did.