Lines and columns flip randomly using Compiz and wall plugin

I'm using fully patched Lucid (but I have that bug for years).

Using the wall effect with Compiz (4*4 desktop), when I'm changing of desktop, it *sometimes* flips two lines or two colomn, or it moves all the columns by one on the left : every windows are displaced.

I do not know how to reproduce it reliably, but I got that one or two times a day.

As an example, let say that my windows A,B,C,D, E and F are on the following desktops (* are for empy desktops) :

ADF
B**
*E*

at a certain point, I got the situation

ADF
*E*
B**
(flip line 2 and 3)

or

FAD
*B*
**E
(everybody one column right)

Please feel free to ask any further informations or tests because I have no idea of what triggers.

ProblemType: Bug
DistroRelease: Ubuntu 10.04
Package: compiz 1:0.8.4-0ubuntu13
ProcVersionSignature: Ubuntu 2.6.32-18.27-generic 2.6.32.10+drm33.1
Uname: Linux 2.6.32-18-generic i686
NonfreeKernelModules: nvidia
Architecture: i386
CompizPlugins: [core,ccp,dbus,place,mousepoll,gnomecompat,move,resize,decoration,png,svg,imgjpeg,text,commands,neg,wall,snap,animation,scale,scaleaddon,expo,staticswitcher,regex,resizeinfo,workarounds,ezoom,vpswitch,fade,session]
CurrentDmesg:
 [ 17.067414] ppdev: user-space parallel port driver
 [ 27.292514] eth0: no IPv6 routers present
 [ 56.784970] CPUFREQ: Per core ondemand sysfs interface is deprecated - up_threshold
Date: Wed Mar 31 11:52:57 2010
InstallationMedia: Kubuntu 10.04 "Lucid Lynx" - Beta i386 (20100317)
MachineType: Dell Inc. Inspiron 530
PackageArchitecture: all
PciDisplay: 01:00.0 VGA compatible controller [0300]: nVidia Corporation G86 [GeForce 8300 GS] [10de:0423] (rev a1)
ProcCmdLine: BOOT_IMAGE=/boot/vmlinuz-2.6.32-18-generic root=UUID=1572a37a-f8db-4fa7-893c-728f5bb1c5fe ro quiet splash
ProcEnviron:
 LANGUAGE=
 PATH=(custom, no user)
 LANG=it_IT.UTF-8
 SHELL=/bin/bash
RelatedPackageVersions:
 xserver-xorg 1:7.5+3ubuntu1
 libgl1-mesa-glx 7.7-4ubuntu1
 libdrm2 2.4.18-1ubuntu2
 xserver-xorg-video-intel 2:2.9.1-1ubuntu18
 xserver-xorg-video-ati 1:6.12.192-2ubuntu1
SourcePackage: compiz
dmi.bios.date: 07/12/2007
dmi.bios.vendor: Dell Inc.
dmi.bios.version: 1.0.3
dmi.board.name: 0RY007
dmi.board.vendor: Dell Inc.
dmi.board.version: ���
dmi.chassis.type: 3
dmi.chassis.vendor: Dell Inc.
dmi.chassis.version: OEM
dmi.modalias: dmi:bvnDellInc.:bvr1.0.3:bd07/12/2007:svnDellInc.:pnInspiron530:pvr:rvnDellInc.:rn0RY007:rvr:cvnDellInc.:ct3:cvrOEM:
dmi.product.name: Inspiron 530
dmi.sys.vendor: Dell Inc.
system: distro = Ubuntu, architecture = i686, kernel = 2.6.32-18-generic