Moving vimfiles location breaks snipmate.vim?

Question

I'm working on moving my whole vim config to my Dropbox folder in order share it between machines more effectively. To do this, I've changed my .vimrc to the following:

set runtimepath+=$HOME/My\ Documents/Dropbox/vim
source $HOME\My Documents\Dropbox\vim\vimrc.vim

vimrc.vim looks like this:

set nocompatible
filetype on
filetype plugin on
filetype indent on
syntax enable

The problem is then that snipMate.vim no longer works. I know that there aren't any plugins interfering with it, as I've done a fresh install of vim and removed all the other plugins. It worked perfectly before I moved the plugins to the dropbox folder. I think it may have something to do with the fact that the after directory in vimfiles doesn't seem to be getting read once I move the plugin folder to the dropbox (i.e. after/snipmate.vim only shows up in :scriptnames when I have vimfiles as the plugin folder). I've tried explicitly sourcing the script in the after directory by adding the following to my .vimrc:

source $HOME\My Documents\Dropbox\vim\after\plugin\snipMate.vim

but snipmate still doesn't work.

Any ideas on fixing this?