Comment 2 for bug 1304067

Presumably this is Pantheons or Switchboard's fault and since I could repro your problem, this need further attention by the developers of ElementaryOS and probably Pantheon in particular.

For the time being, I devised this workaround:

Open a Terminal Window and type:

1) sudo update-alternatives --config x-cursor-theme
2) Select "6" for White
3) Go back to 1) but this time select "5"
4) sudo apt-get install dconf-tools
5) dconf-editor
6) Goto Org -> Gnome -> Desktop -> Interface, change whatever String there is in "cursor-theme" to "DMZ-Black".
7) make sure "curser-size" is set to "24".
8) Reboot

Your Mouse Cursor should be back to normal now.