Blender hangs on default cube texture paint in 3d view

As subject goes - buildbot builds from last 3 or so days - linux, 64 bit. nvidia GTX 560 2Gb, driver 331.20
Blender render, mark seams, unwrap, assign new 1k image, no alpha, Material and Texture as this image mapped to UV.
I can texture paint in UV editor; as soon as i try to do this in 3d view CPU goes haywire, 130%, and there is no more response from Blender. Have to kill process.

Last build working blender-2.70-e2cbfb7-linux-glibc211-x86_64

Smart UV unwrap takes all UV space - it used to be 6 squares, now its 6 rectangles for the default cube: is this correct behavior?

This is not correct behaviour at all, it affects the 2.70 and 2.70a stable too, and according to campbellbarton :

In fact this looks like a float precision issue, if you chance the margin the result flickers back and fourth.

the bug report was there and still not fixed :

Thanks Sanctuary, i thought it might have had changed… no idea what the algorithms are involved but by my brute force calculations that would be 0.66666666 of the total 1 UV space what cube faces would take if they were squares - 0.1111111 each.
Imho even weird Python rounding shouldn’t do this (but this is C here likely). Well, let’s hope it flickers back again ;).
I wonder what happens with shapes different from this corner case meanwhile.

Cube can be painted again in today’s build - blender-2.70-0f91d2c-linux-glibc211-x86_64.

Yes, good news, CambellBarton have fixed it ,i will have to try with a new build tomorrow