Edge resistence inconsistent in multiscreen

Ubuntu 12.10, unity 6.6, nvidia dual screen.
I want to hit cog icon in the top right of the left screen but I overshoot to the right screen and come back for another go. It seems that if the mouse keeps moving as I'm trying to hit the target, the edge resistence between screens doesn't kick in. if I stop the mouse dead, then move towards the edge, the edge resistence works again. Easily reproduced and here's a video showing it..

http://www.youtube.com/watch?v=hKYIuB8Xqt8

ProblemType: Bug
DistroRelease: Ubuntu 12.10
Package: unity 6.6.0-0ubuntu1
ProcVersionSignature: Ubuntu 3.5.0-16.24-generic 3.5.4
Uname: Linux 3.5.0-16-generic x86_64
NonfreeKernelModules: nvidia
ApportVersion: 2.5.3-0ubuntu1
Architecture: amd64
CompizPlugins: [core,composite,opengl,compiztoolbox,decor,vpswitch,snap,mousepoll,resize,place,move,wall,grid,regex,imgpng,session,gnomecompat,animation,fade,unitymtgrabhandles,workarounds,scale,expo,ezoom,unityshell]
Date: Sat Sep 29 00:31:01 2012
EcryptfsInUse: Yes
InstallationMedia: Ubuntu 12.04 LTS "Precise Pangolin" - Alpha amd64 (20120215)
ProcEnviron:
 LANGUAGE=en_GB:en
 TERM=xterm
 PATH=(custom, no user)
 LANG=en_GB.UTF-8
 SHELL=/bin/bash
SourcePackage: unity
UpgradeStatus: Upgraded to quantal on 2012-08-29 (30 days ago)