UV broken after changin object origin

So, I have a simple object (cube->z=0.5; x,y=10), but after I’ve changed the origin of the object and UV unwrap, I get incorrect UV’s. Object have rotation and scale applied. Using Blender 2.73a.

I’ve put a screenshot.

Seems if you touch the origin of the object you get different results every time in UV, also playing with UV island margin you get distorted UV. Is this a bug or there is a way to avoid this?