Ubuntu 11.04 beta2: Freeze while watching a video

Hello,
When I watch a video, sometimes (about every 30 seconds), it just freeze, and play again and again the same last seconds of the video, just like it was a loop. And, when I move the mouse, it just stop doing that and just continue to play the video.
I really think that's a driver problem as I have that problem with with all video player, including vlc. I actually use the "nouveau" driver. I wanted to try with the NVIDIA drivers, but when I install it, the computer just freeze at gdm login. I also tried to install the .run NVIDIA driver, to see if it works with it, but I just didn't succeed on installing it : it says that I have to remove nouveau, which I did.
My graphic chipset is a 9800MGT.
I'm going to try with the generic video drivers, and I'll add the result in comment of that bug.
Thanks

ProblemType: Bug
DistroRelease: Ubuntu 11.04
Package: xorg 1:7.6+4ubuntu3
ProcVersionSignature: Ubuntu 2.6.38-8.42-generic 2.6.38.2
Uname: Linux 2.6.38-8-generic x86_64
Architecture: amd64
CompizPlugins: [core,bailer,detection,composite,opengl,decor,mousepoll,vpswitch,regex,animation,snap,expo,move,compiztoolbox,place,grid,imgpng,gnomecompat,wall,ezoom,workarounds,staticswitcher,resize,fade,unitymtgrabhandles,scale,session,unityshell]
CompositorRunning: compiz
DRM.card0.DVI.D.1:
 status: disconnected
 enabled: disabled
 dpms: Off
 modes:
 edid-base64:
DRM.card0.LVDS.1:
 status: connected
 enabled: enabled
 dpms: On
 modes: 1680x1050 1680x1050 1400x1050 1280x1024 1280x960 1152x864 1024x768 800x600 640x480 720x400 640x400 640x350
 edid-base64: AP///////wAGEHKcAAAAAA8RAQOAJRd4ClwgmFhRjiUiUFQAAAABAQEBAQEBAQEBAQEBAQEBfC6QoGAaHkAwIDYAb+YQAAAYAAAAAQAGEDAAAAAAAAAAAAogAAAA/gBMUDE3MVdFMi1UTEEzAAAA/gBDb2xvciBMQ0QKICAgAHg=
DRM.card0.VGA.1:
 status: disconnected
 enabled: disabled
 dpms: Off
 modes:
 edid-base64:
Date: Mon Apr 18 14:16:58 2011
DistUpgraded: Fresh install
DistroCodename: natty
DistroVariant: ubuntu
DkmsStatus: virtualbox-ose, 4.0.4, 2.6.38-8-generic, x86_64: installed
EcryptfsInUse: Yes
GraphicsCard:
 nVidia Corporation G92 [GeForce 9800M GT] [10de:060b] (rev a2) (prog-if 00 [VGA controller])
   Subsystem: CLEVO/KAPOK Computer Device [1558:0573]
InstallationMedia: Ubuntu 11.04 "Natty Narwhal" - Beta amd64 (20110413)
MachineType: Clevo Co. M570RU
ProcEnviron:
 LANGUAGE=fr_FR:en
 LANG=fr_FR.UTF-8
 SHELL=/bin/bash
ProcKernelCmdLine: BOOT_IMAGE=/boot/vmlinuz-2.6.38-8-generic root=UUID=3ec89063-7641-4b75-9b40-92d2fbca9a9a ro quiet splash vt.handoff=7
Renderer: Unknown
SourcePackage: xorg
Symptom: display
Title: Xorg freeze
UpgradeStatus: No upgrade log present (probably fresh install)
dmi.bios.date: 01/14/2009
dmi.bios.vendor: Phoenix
dmi.bios.version: SROSA001.86C.
dmi.board.name: SANTA ROSA
dmi.board.vendor: Clevo Co.
dmi.board.version: Not Applicable
dmi.chassis.asset.tag: No Asset Tag
dmi.chassis.type: 1
dmi.chassis.vendor: CLEVO
dmi.chassis.version: N/A
dmi.modalias: dmi:bvnPhoenix:bvrSROSA001.86C.:bd01/14/2009:svnClevoCo.:pnM570RU:pvrCLEVOM570RU-1.00.12:rvnClevoCo.:rnSANTAROSA:rvrNotApplicable:cvnCLEVO:ct1:cvrN/A:
dmi.product.name: M570RU
dmi.product.version: CLEVO:M570RU-1.00.12
dmi.sys.vendor: Clevo Co.
version.compiz: compiz 1:0.9.4+bzr20110415-0ubuntu1
version.ia32-libs: ia32-libs 20090808ubuntu12
version.libdrm2: libdrm2 2.4.23-1ubuntu6
version.libgl1-mesa-dri: libgl1-mesa-dri 7.10.2-0ubuntu1
version.libgl1-mesa-dri-experimental: libgl1-mesa-dri-experimental 7.10.2-0ubuntu1
version.libgl1-mesa-glx: libgl1-mesa-glx 7.10.2-0ubuntu1
version.xserver-xorg: xserver-xorg 1:7.6+4ubuntu3
version.xserver-xorg-video-ati: xserver-xorg-video-ati 1:6.14.0-0ubuntu4
version.xserver-xorg-video-intel: xserver-xorg-video-intel 2:2.14.0-4ubuntu7
version.xserver-xorg-video-nouveau: xserver-xorg-video-nouveau 1:0.0.16+git20110107+b795ca6e-0ubuntu7