Launcher scroll does fails to function properly

week 30 -Release ubuntu 12.10 quantal (Nvidia) with ppa:SIL2100

Launcher fails to scroll when an icon is moved towards the trash. User cannot drag an icon directly to trash when there are too many icons on the launcher and some at the bottom are folded. See screenshot, it shows the music player icon being dragged to the bottom end of the screen and the trash icon is still not visible, meaning launcher failed to scroll.

Follow the steps below:
-Ensure the launcher has many icons on it, few icons at the bottom end are folded.
-Drag any icon from the top half of the launcher
- Try to drag it to trash

ProblemType: Bug
DistroRelease: Ubuntu 12.10
Package: unity 6.0.0-0ubuntu5~test1 [origin: LP-PPA-sil2100-quantal]
ProcVersionSignature: Ubuntu 3.5.0-6.6-generic 3.5.0
Uname: Linux 3.5.0-6-generic i686
ApportVersion: 2.4-0ubuntu5
Architecture: i386
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]
CrashDB: unity
Date: Fri Jul 27 14:14:00 2012
InstallationMedia: Ubuntu 12.10 "Quantal Quetzal" - Alpha i386 (20120713.1)
ProcEnviron:
 LANGUAGE=en_GB:en
 TERM=xterm
 PATH=(custom, no user)
 LANG=en_GB.UTF-8
 SHELL=/bin/bash
SourcePackage: unity
UpgradeStatus: No upgrade log present (probably fresh install)