I'm running Ubuntu 10.04 64-bit and cairo-dock 2.3.0~2.  Gnome is the desktop manager, Compiz/Emerald is my window manager.  Cairo-dock is running openGL on Intel HD (i3).  Sorry, not sure how to look up the drivers in use...
This bug occurs whenever cairo-dock is open and rhythmbox is initiated.  Fist I opened the terminal and started cairo-dock.  Then, opened a tab and started rhythmbox.  Here's both tab's results:
laptop:~$ cairo-dock -o
warning :  (/build/buildd/cairo-dock-2.3.0~2/src/gldit/cairo-dock-opengl.c:cairo_dock_initialize_opengl_backend:171)  
  couldn't find an appropriate visual, trying to get one without Stencil buffer
(it may cause some little deterioration in the rendering) ...

 ============================================================================ 
	Cairo-Dock version: 2.3.0~2
	Compiled date:  May 29 2011 11:40:02
	Running with OpenGL: 1
 ============================================================================

warning :  (/build/buildd/cairo-dock-2.3.0~2/src/gldit/cairo-dock-module-manager.c:cairo_dock_load_module:167)  
  while opening module '/usr/lib/cairo-dock/libcd_xfce-integration.so' : (libthunar-vfs-1.so.2: cannot open shared object file: No such file or directory)
warning :  (/build/buildd/cairo-dock-2.3.0~2/src/gldit/cairo-dock-packages.c:cairo_dock_list_packages:699)  
  while listing user packages in '/home/justin/.config/cairo-dock/third-party' : Error opening directory '/home/justin/.config/cairo-dock/third-party': No such file or directory
_cd_find_volume_name_from_drive_name: assertion `pDrive != NULL' failed
_cd_find_volume_name_from_drive_name: assertion `pDrive != NULL' failed
do_wait: drmWaitVBlank returned -1, IRQs don't seem to be working correctly.
Try adjusting the vblank_mode configuration parameter.
warning :  (/build/buildd/cairo-dock-2.3.0~2/src/cairo-dock.c:_cairo_dock_intercept_signal:272)  
  Cairo-Dock has crashed (sig 11).
It will be restarted now (cairo-dock -o).
Feel free to report this bug on glx-dock.org to help improving the dock !
info on the system :
Linux Zero-laptop 2.6.32-32-generic #62-Ubuntu SMP Wed Apr 20 21:52:38 UTC 2011 x86_64 GNU/Linux
Couldn't guess if it was an applet's fault or not. It may have crashed inside the core or inside a thread
warning :  (/build/buildd/cairo-dock-2.3.0~2/src/gldit/cairo-dock-opengl.c:cairo_dock_initialize_opengl_backend:171)  
  couldn't find an appropriate visual, trying to get one without Stencil buffer
(it may cause some little deterioration in the rendering) ...

 ============================================================================ 
	Cairo-Dock version: 2.3.0~2
	Compiled date:  May 29 2011 11:40:02
	Running with OpenGL: 1
 ============================================================================

warning :  (/build/buildd/cairo-dock-2.3.0~2/src/gldit/cairo-dock-module-manager.c:cairo_dock_load_module:167)  
  while opening module '/usr/lib/cairo-dock/libcd_xfce-integration.so' : (libthunar-vfs-1.so.2: cannot open shared object file: No such file or directory)
warning :  (/build/buildd/cairo-dock-2.3.0~2/src/gldit/cairo-dock-packages.c:cairo_dock_list_packages:699)  
  while listing user packages in '/home/justin/.config/cairo-dock/third-party' : Error opening directory '/home/justin/.config/cairo-dock/third-party': No such file or directory
_cd_find_volume_name_from_drive_name: assertion `pDrive != NULL' failed
_cd_find_volume_name_from_drive_name: assertion `pDrive != NULL' failed
do_wait: drmWaitVBlank returned -1, IRQs don't seem to be working correctly.
Try adjusting the vblank_mode configuration parameter.
warning :  (/build/buildd/cairo-dock-2.3.0~2/src/cairo-dock.c:_cairo_dock_intercept_signal:272)  
  Cairo-Dock has crashed (sig 11).
It will be restarted now (cairo-dock -o -m).
Feel free to report this bug on glx-dock.org to help improving the dock !
info on the system :
Linux Zero-laptop 2.6.32-32-generic #62-Ubuntu SMP Wed Apr 20 21:52:38 UTC 2011 x86_64 GNU/Linux
Couldn't guess if it was an applet's fault or not. It may have crashed inside the core or inside a thread
warning :  (/build/buildd/cairo-dock-2.3.0~2/src/gldit/cairo-dock-opengl.c:cairo_dock_initialize_opengl_backend:171)  
  couldn't find an appropriate visual, trying to get one without Stencil buffer
(it may cause some little deterioration in the rendering) ...

 ============================================================================ 
	Cairo-Dock version: 2.3.0~2
	Compiled date:  May 29 2011 11:40:02
	Running with OpenGL: 1
 ============================================================================

warning :  (/build/buildd/cairo-dock-2.3.0~2/src/gldit/cairo-dock-module-manager.c:cairo_dock_load_module:167)  
  while opening module '/usr/lib/cairo-dock/libcd_xfce-integration.so' : (libthunar-vfs-1.so.2: cannot open shared object file: No such file or directory)
g_key_file_set_string: assertion `string != NULL' failed
g_key_file_set_string: assertion `string != NULL' failed
g_key_file_set_string: assertion `string != NULL' failed
g_key_file_set_string: assertion `string != NULL' failed
cairo_dock_set_status_message ()
cairo_dock_set_status_message (Listing themes in 'themes2.2' ...)
cairo_dock_set_status_message ()
showing the maintenance mode ...
cairo_dock_set_status_message ()
Next tab:
-laptop:~$ rhythmbox

(rhythmbox:7540): GdkPixbuf-CRITICAL **: gdk_pixbuf_new_from_file_at_scale: assertion `filename != NULL' failed

(rhythmbox:7540): GLib-GObject-CRITICAL **: g_object_unref: assertion `G_IS_OBJECT (object)' failed
Traceback (most recent call last):
  File "/usr/lib/rhythmbox/plugins/umusicstore/__init__.py", line 58, in activate
    icon = gtk.gdk.pixbuf_new_from_file_at_size(icon_file_name, 22, 22)
TypeError: pixbuf_new_from_file_at_size() argument 1 must be string, not None
** (rhythmbox:7540): DEBUG: Loading the real store page

** (rhythmbox:7540): WARNING **: Syncdaemon already connected, not connecting again

liboauth: data to sign='GET&https%3A%2F%2Fone.ubuntu.com%2Fmusic%2Flogin&oauth_callback%3DNone%26oauth_consumer_key%3Dubuntuone%26oauth_nonce%3DsQZEHpXsjANIUwLVdrfE4w2eCUw%26oauth_signature_method%3DHMAC-SHA1%26oauth_timestamp%3D1308067203%26oauth_token%3DdqSMRVP47pVRsQdZZNvg%26oauth_verifier%3DNone%26oauth_version%3D1.0'


liboauth: key='hammertime&5Rbkx1Px3RTPlm6g1Rcc100J31kwqXF044sC5qGK62hkTk7BwXjxJQnDJ7Xbwgbdz09V2d6GdCDk7rX3'

** (rhythmbox:7540): DEBUG: navigation requested to https://one.ubuntu.com/music/login?oauth_callback=None&oauth_consumer_key=ubuntuone&oauth_nonce=sQZEHpXsjANIUwLVdrfE4w2eCUw&oauth_signature_method=HMAC-SHA1&oauth_timestamp=1308067203&oauth_token=dqSMRVP47pVRsQdZZNvg&oauth_verifier=None&oauth_version=1.0&oauth_signature=2y3nuNKQWJGAtnrOfIwalB%2BO%2FHU%3D
** (rhythmbox:7540): DEBUG: navigation requested to http://stores.7digital.com/user/partnerLogin.aspx?shop=480&returnUrl=http%3A%2F%2Fstores.7digital.com%2Fdefault.aspx%3Fshop%3D480%26partner%3D983&oauth_nonce=85801228&oauth_timestamp=1308067204&oauth_signature_method=HMAC-SHA1&oauth_consumer_key=canonical&userid=246735&oauth_version=1.0&oauth_signature=FIiPQTbUffqKH2OK2dRj6lIX4TQ%3D&partner=983
** (rhythmbox:7540): DEBUG: navigation requested to http://stores.7digital.com/default.aspx?shop=480&partner=983
laptop:~$ cairo-dock -o
warning :  (/build/buildd/cairo-dock-2.3.0~2/src/gldit/cairo-dock-opengl.c:cairo_dock_initialize_opengl_backend:171)  
  couldn't find an appropriate visual, trying to get one without Stencil buffer
(it may cause some little deterioration in the rendering) ...

 ============================================================================ 
	Cairo-Dock version: 2.3.0~2
	Compiled date:  May 29 2011 11:40:02
	Running with OpenGL: 1
 ============================================================================

warning :  (/build/buildd/cairo-dock-2.3.0~2/src/gldit/cairo-dock-module-manager.c:cairo_dock_load_module:167)  
  while opening module '/usr/lib/cairo-dock/libcd_xfce-integration.so' : (libthunar-vfs-1.so.2: cannot open shared object file: No such file or directory)
warning :  (/build/buildd/cairo-dock-2.3.0~2/src/gldit/cairo-dock-packages.c:cairo_dock_list_packages:699)  
  while listing user packages in '/home/justin/.config/cairo-dock/third-party' : Error opening directory '/home/justin/.config/cairo-dock/third-party': No such file or directory
_cd_find_volume_name_from_drive_name: assertion `pDrive != NULL' failed
_cd_find_volume_name_from_drive_name: assertion `pDrive != NULL' failed
do_wait: drmWaitVBlank returned -1, IRQs don't seem to be working correctly.
Try adjusting the vblank_mode configuration parameter.
warning :  (/build/buildd/cairo-dock-2.3.0~2/src/cairo-dock.c:_cairo_dock_intercept_signal:272)  
  Cairo-Dock has crashed (sig 11).
It will be restarted now (cairo-dock -o).
Feel free to report this bug on glx-dock.org to help improving the dock !
info on the system :
Linux Zero-laptop 2.6.32-32-generic #62-Ubuntu SMP Wed Apr 20 21:52:38 UTC 2011 x86_64 GNU/Linux
Couldn't guess if it was an applet's fault or not. It may have crashed inside the core or inside a thread
warning :  (/build/buildd/cairo-dock-2.3.0~2/src/gldit/cairo-dock-opengl.c:cairo_dock_initialize_opengl_backend:171)  
  couldn't find an appropriate visual, trying to get one without Stencil buffer
(it may cause some little deterioration in the rendering) ...

 ============================================================================ 
	Cairo-Dock version: 2.3.0~2
	Compiled date:  May 29 2011 11:40:02
	Running with OpenGL: 1
 ============================================================================

warning :  (/build/buildd/cairo-dock-2.3.0~2/src/gldit/cairo-dock-module-manager.c:cairo_dock_load_module:167)  
  while opening module '/usr/lib/cairo-dock/libcd_xfce-integration.so' : (libthunar-vfs-1.so.2: cannot open shared object file: No such file or directory)
warning :  (/build/buildd/cairo-dock-2.3.0~2/src/gldit/cairo-dock-packages.c:cairo_dock_list_packages:699)  
  while listing user packages in '/home/justin/.config/cairo-dock/third-party' : Error opening directory '/home/justin/.config/cairo-dock/third-party': No such file or directory
_cd_find_volume_name_from_drive_name: assertion `pDrive != NULL' failed
_cd_find_volume_name_from_drive_name: assertion `pDrive != NULL' failed
do_wait: drmWaitVBlank returned -1, IRQs don't seem to be working correctly.
Try adjusting the vblank_mode configuration parameter.
warning :  (/build/buildd/cairo-dock-2.3.0~2/src/cairo-dock.c:_cairo_dock_intercept_signal:272)  
  Cairo-Dock has crashed (sig 11).
It will be restarted now (cairo-dock -o -m).
Feel free to report this bug on glx-dock.org to help improving the dock !
info on the system :
Linux Zero-laptop 2.6.32-32-generic #62-Ubuntu SMP Wed Apr 20 21:52:38 UTC 2011 x86_64 GNU/Linux
Couldn't guess if it was an applet's fault or not. It may have crashed inside the core or inside a thread
warning :  (/build/buildd/cairo-dock-2.3.0~2/src/gldit/cairo-dock-opengl.c:cairo_dock_initialize_opengl_backend:171)  
  couldn't find an appropriate visual, trying to get one without Stencil buffer
(it may cause some little deterioration in the rendering) ...

 ============================================================================ 
	Cairo-Dock version: 2.3.0~2
	Compiled date:  May 29 2011 11:40:02
	Running with OpenGL: 1
 =====

If there's anything I can do to help solve this issue please let me know.