Screen freezes when dragging a selection of bookmarks in Firefox

[Lem]

This is easily reproducible under Unity3D.

* Start Firefox.
* Menu: Bookmarks -> Show All Bookmarks
* Select a range of 5-10 bookmarks
* Drag bookmarks around the screen, move them for at least 20 seconds.
* Screen should freeze after about 0.5-1 second, then freeze for a variable 5-20 seconds depending on individual computer (watch the clock indicator to know it's frozen if no other activity is occurring)
* Once the screen unfreezes, the Unity panel will grey out some icons and leave others alone (looks like it should do that for drag and drop functionality), and the drag/drop event can be completed.

Tested on an AMD Phenom II 955 with nVidia GTX560Ti (NVIDIA Corporation GF110 [GeForce GTX 560 Ti] (rev a1)) using nvidia binary driver, and Core 2 Duo with Intel onboard GPU (Intel Corporation 82946GZ/GL Integrated Graphics Controller (rev 02)).

There is a 5 second freeze with 10 bookmarks on the Phenom II, and a ~20 second stall on the Core 2 Duo.

This does not occur under Unity2D over VNC.

ProblemType: Bug
DistroRelease: Ubuntu 12.04
Package: unity 5.12-0ubuntu1.1
ProcVersionSignature: Ubuntu 3.2.0-25.40-generic 3.2.18
Uname: Linux 3.2.0-25-generic x86_64
NonfreeKernelModules: nvidia
ApportVersion: 2.0.1-0ubuntu9
Architecture: amd64
CompizPlugins: [core,composite,opengl,decor,grid,snap,resize,place,move,mousepoll,commands,session,wall,compiztoolbox,gnomecompat,regex,imgpng,vpswitch,unitymtgrabhandles,animation,fade,expo,workarounds,ezoom,scale,unityshell]
Date: Wed Jun 13 12:50:28 2012
InstallationMedia: Ubuntu 12.04 LTS "Precise Pangolin" - Beta amd64 (20120301)
SourcePackage: unity
UpgradeStatus: No upgrade log present (probably fresh install)

[Lem (lem-jjr)]

I should have also mentioned that this freeze doesn't appear to occur when dragging a single bookmark, however the freeze gets progressively longer with 2, 3 and 4 bookmarks. But, but the time 5-10 are selected, the freeze seems to be the same duration..

[Launchpad Janitor (janitor)]

Status changed to 'Confirmed' because the bug affects multiple users.

[Omer Akram (om26er)]

Thanks for the bug report. This particular bug has already been reported and is a duplicate of bug 772445, so is being marked as such. Any further discussion regarding the bug should occur in the other report. Feel free to report any other bugs you may find.