WTF? Separated object somehow linked to original mesh's translation

Blend Here:

Something is weird here. Not sure if it’s me, or something in the build I’m using.
This is Blender 2.62 Trunk for mac
trying to model with BMESH.
(I think the model is currently Ngon free though, it opens in vanilla 2.62)

I made the crappy box modeled mouse mesh with the dark material.
I started the better mousehead object inside the first one in Edit mode, then used P to Separate by Selection.
Then I had two mesh objects. They don’t seem to be linked or constrained or parented to each other in any way I can tell, but when I translate either object, they both move?

WTF did I do wrong? I’ve never ran into this when Separating a part of a mesh into a new object.

You have Proportional Editing enabled in Object Mode, with a very high effect radius. Set it to None and the objects can be moved separately.

Hotkey for Proportional Editing is O-KEY (it’s a toggle, btw), so it’s fairly easy to accidentally enable it.

oh jeez

officially hanging my head in shame.

Thanks Chipmasque.