Well, actually I managed to make it work: I have removed the configuration file (.PlaneShift), reinstalled the game, and set the option Video.FullScreen = true in the configuration files (pslaunch.cfg and psclient.cfg).
Not sure of which action solved the issue though.
But I still cannot start the game: when I press 'Play', the window disapears and I am left with lots of errors in the console. I am not sure about the 'pandemonium will ensue.' message, and there is a very bad problem at the end (X Error of failed request: BadWindow (invalid Window parameter)).
Any suggestion?
:~/Applications/PlaneShift$ ./pslaunch
WARNING: could not load plugin 'crystalspace.syntax.loader.service.text'
ERROR: Couldn't load plugin with class 'crystalspace.syntax.loader.service.text'!
WARNING: failed to initialize plugin 'crystalspace.graphics3d.shadercompiler.xmlshader'
WARNING: failed to initialize plugin 'crystalspace.graphics3d.shadercompiler.weaver'
WARNING: could not load plugin 'crystalspace.syntax.loader.service.text'
ERROR: Couldn't load plugin with class 'crystalspace.syntax.loader.service.text'!
WARNING: failed to initialize plugin 'crystalspace.graphics3d.shadercompiler.xmlshader'
WARNING: could not load plugin 'crystalspace.level.loader'
WARNING: could not load plugin 'crystalspace.level.loader'
WARNING: Can not load default shader vars, no iSyntaxService available
Opening GLX2D
Checking for updates to the updater: Using mirror http://planeshift.clevertech.net/Updates/ for updaterinfo.xml
Creating Context
FULL SCREEN: 1024, 768
Video driver GL/X version (direct renderer)
Visual ID: 0x0000000000000027, 24bit TrueColor
R8:G8:B8:A8,
level 0, double buffered
WARNING: could not load plugin 'crystalspace.syntax.loader.service.text'
ERROR: Couldn't load plugin with class 'crystalspace.syntax.loader.service.text'!
NOTIFY: Applied: Broken ATI point sprites (ATI)
NOTIFY: Applied: ATI: Can't handle compressed formats for RECT textures
NOTIFY: Applied: ATI: RECT texture extension support apparently sucks
NOTIFY: Applied: ATI: 'Forceful' fixed function enable
NOTIFY: OpenGL renderer: ATI Radeon HD 4250 (vendor: ATI Technologies Inc.) version 3.3.10428 Compatibility Profile Context
NOTIFY: Using full screen mode at resolution 1024x768.
NOTIFY: Pixel format: Color: 24 Alpha: 8 Depth: 24 Stencil: 8 AccumColor: 0 AccumAlpha: 0 MultiSamples: 0
NOTIFY: Multisample: disabled
NOTIFY: Using VBO with 64 MB of VBO memory
Default shader /shader/std_lighting.xml not available
/shader/std_lighting_portal.xml: 'xmlshader' shader compiler not available
Default shader /shader/std_lighting_portal.xml not available
WARNING: could not load plugin 'crystalspace.renderloop.step.generic.type'
Failed to load plugin crystalspace.renderloop.step.generic.type; pandemonium will ensue.
WARNING: could not load plugin 'crystalspace.rendermanager.unshadowed'
No rendermanager set!
Mounting skin: /planeshift/art/pslaunch.zip
Texture Manager parsing /paws/launcher/imagelist.xml
Wed Feb 9 19:09:30 2011, <src/common/paws/pawsimagedrawable.cpp:66 PreparePixmap SEVERE>
Wed Feb 9 19:09:30 2011, Could not open image: >/paws/base/maps/leather/top_left_1.png<
Wed Feb 9 19:09:30 2011, <src/common/paws/pawsimagedrawable.cpp:66 PreparePixmap SEVERE>
Wed Feb 9 19:09:30 2011, Could not open image: >/paws/base/maps/leather/top_right_1.png<
Wed Feb 9 19:09:30 2011, <src/common/paws/pawsimagedrawable.cpp:66 PreparePixmap SEVERE>
Wed Feb 9 19:09:30 2011, Could not open image: >/paws/base/maps/leather/bottom_left_1.png<
Wed Feb 9 19:09:30 2011, <src/common/paws/pawsimagedrawable.cpp:66 PreparePixmap SEVERE>
Wed Feb 9 19:09:30 2011, Could not open image: >/paws/base/maps/leather/bottom_right_1.png<
Wed Feb 9 19:09:30 2011, <src/common/paws/pawsimagedrawable.cpp:66 PreparePixmap SEVERE>
Wed Feb 9 19:09:30 2011, Could not open image: >/paws/base/maps/leather/left_1.png<
Wed Feb 9 19:09:30 2011, <src/common/paws/pawsimagedrawable.cpp:66 PreparePixmap SEVERE>
Wed Feb 9 19:09:30 2011, Could not open image: >/paws/base/maps/leather/right_1.png<
Wed Feb 9 19:09:30 2011, <src/common/paws/pawsimagedrawable.cpp:66 PreparePixmap SEVERE>
Wed Feb 9 19:09:30 2011, Could not open image: >/paws/base/maps/leather/top_1.png<
Wed Feb 9 19:09:30 2011, <src/common/paws/pawsimagedrawable.cpp:66 PreparePixmap SEVERE>
Wed Feb 9 19:09:30 2011, Could not open image: >/paws/base/maps/leather/bottom_1.png<
Wed Feb 9 19:09:30 2011, <src/common/sound/system.cpp:36 Initialize SEVERE>
Wed Feb 9 19:09:30 2011, Failed to locate Sound renderer!
DEBUG: Initializing OpenAL sound system
DEBUG: Retrieving available devices.
DEBUG: Available OpenAL device: PulseAudio Software
DEBUG: Available OpenAL device: ALSA Software
DEBUG: Available OpenAL device: OSS Software
DEBUG: Default OpenAL device: PulseAudio Software
DEBUG: No device specified
DEBUG: Falling back on default device
DEBUG: OpenAL context frequency: 44100 Hz
DEBUG: OpenAL context refresh: 21 Hz
DEBUG: OpenAL context uses asynchronous (threaded) context
DEBUG: OpenAL context should support 255 mono sources
DEBUG: OpenAL context should support 1 stereo sources
Couldn't locate resource Examine Background in the current skin!
Couldn't locate resource Examine Background in the current skin!
Using mirror http://216.6.227.163/updater/ for updaterinfo.xml
Using mirror http://216.6.227.163/updater/ for updateservers.xml
No updates needed!
Checking for updates to all files: No updates needed!
DEBUG: Initializing OpenAL sound system
DEBUG: Retrieving available devices.
DEBUG: Available OpenAL device: PulseAudio Software
DEBUG: Available OpenAL device: ALSA Software
DEBUG: Available OpenAL device: OSS Software
DEBUG: Default OpenAL device: PulseAudio Software
DEBUG: No device specified
DEBUG: Falling back on default device
DEBUG: OpenAL context frequency: 44100 Hz
DEBUG: OpenAL context refresh: 21 Hz
DEBUG: OpenAL context uses asynchronous (threaded) context
DEBUG: OpenAL context should support 255 mono sources
DEBUG: OpenAL context should support 1 stereo sources
Couldn't locate resource Examine Background in the current skin!
Couldn't locate resource Examine Background in the current skin!
DEBUG: Closing OpenAL sound system
X Error of failed request: BadWindow (invalid Window parameter)
Major opcode of failed request: 4 (X_DestroyWindow)
Resource id in failed request: 0x3e00003
Serial number of failed request: 504
Current serial number in output stream: 506
AL lib: ALc.c:1879: exit(): closing 1 Device