Maybe, you need a different VIEW (for each client?).
While 'player' is the "Global pointer to the player entity on the current machine."[from the manual], camera doesn't get such a definition...

http://www.puppenheim.org/
http://www.wuerfels-welt.de
Old Game Tutorial: http://www.puppenheim.org/MITutorial.zip
Free Game Editor: http://puppenheim.org/AlienalsWeihnachtsmann.zip
http://www.puppenheim.org/blender_starting_main_settings.txt