Now it starts Alice, but when I open a world it gives me a brief glimpse of the scene in the world window, and then it turns black, and the rest of the screen blanks out.

When I run it in the terminal, I get a bunch of error messages before Alice starts, and no further error messages when I attempt to start a world:

attempting to register mp3 capability...
Registered succesfully
*sys-package-mgr*: processing modified jar, '/usr/lib/jvm/java-1.5.0-sun-1.5.0.16/jre/lib/rt.jar'
*sys-package-mgr*: can't write cache file for '/usr/lib/jvm/java-1.5.0-sun-1.5.0.16/jre/lib/rt.jar'
*sys-package-mgr*: processing modified jar, '/usr/lib/jvm/java-1.5.0-sun-1.5.0.16/jre/lib/jsse.jar'
*sys-package-mgr*: can't write cache file for '/usr/lib/jvm/java-1.5.0-sun-1.5.0.16/jre/lib/jsse.jar'
*sys-package-mgr*: processing modified jar, '/usr/lib/jvm/java-1.5.0-sun-1.5.0.16/jre/lib/jce.jar'
*sys-package-mgr*: can't write cache file for '/usr/lib/jvm/java-1.5.0-sun-1.5.0.16/jre/lib/jce.jar'
*sys-package-mgr*: processing modified jar, '/usr/lib/jvm/java-1.5.0-sun-1.5.0.16/jre/lib/charsets.jar'
*sys-package-mgr*: can't write cache file for '/usr/lib/jvm/java-1.5.0-sun-1.5.0.16/jre/lib/charsets.jar'
*sys-package-mgr*: processing modified jar, '/usr/lib/jvm/java-1.5.0-sun-1.5.0.16/jre/lib/ext/dnsns.jar'
*sys-package-mgr*: can't write cache file for '/usr/lib/jvm/java-1.5.0-sun-1.5.0.16/jre/lib/ext/dnsns.jar'
*sys-package-mgr*: processing modified jar, '/usr/lib/jvm/java-1.5.0-sun-1.5.0.16/jre/lib/ext/sunjce_provider.jar'
*sys-package-mgr*: can't write cache file for '/usr/lib/jvm/java-1.5.0-sun-1.5.0.16/jre/lib/ext/sunjce_provider.jar'
*sys-package-mgr*: processing modified jar, '/usr/lib/jvm/java-1.5.0-sun-1.5.0.16/jre/lib/ext/localedata.jar'
*sys-package-mgr*: can't write cache file for '/usr/lib/jvm/java-1.5.0-sun-1.5.0.16/jre/lib/ext/localedata.jar'
*sys-package-mgr*: processing modified jar, '/usr/lib/jvm/java-1.5.0-sun-1.5.0.16/jre/lib/ext/sunpkcs11.jar'
*sys-package-mgr*: can't write cache file for '/usr/lib/jvm/java-1.5.0-sun-1.5.0.16/jre/lib/ext/sunpkcs11.jar'
Locking assertion failure. Backtrace:
#0 /usr/lib/libxcb-xlib.so.0 [0x7fb78d6f99fc]
#1 /usr/lib/libxcb-xlib.so.0(xcb_xlib_unlock+0x24) [0x7fb78d6f9ab4]
#2 /usr/lib/libX11.so.6(_XReply+0x268) [0x7fb78db47698]
#3 /usr/lib/jvm/java-1.5.0-sun-1.5.0.16/jre/lib/amd64/xawt/libmawt.so [0x7fb78e053d7b]
#4 /usr/lib/jvm/java-1.5.0-sun-1.5.0.16/jre/lib/amd64/xawt/libmawt.so [0x7fb78e040e9c]
#5 /usr/lib/jvm/java-1.5.0-sun-1.5.0.16/jre/lib/amd64/xawt/libmawt.so [0x7fb78e040ffe]
#6 /usr/lib/jvm/java-1.5.0-sun-1.5.0.16/jre/lib/amd64/xawt/libmawt.so(Java_sun_awt_X11GraphicsEnvironment_ini tDisplay+0x9) [0x7fb78e0411c9]
#7 [0x7fb7b6360f7b]
Locking assertion failure. Backtrace:
#0 /usr/lib/libxcb-xlib.so.0 [0x7fb78d6f99fc]
#1 /usr/lib/libxcb-xlib.so.0(xcb_xlib_lock+0x17) [0x7fb78d6f9b77]
#2 /usr/lib/libX11.so.6 [0x7fb78db468c0]
#3 /usr/lib/libX11.so.6(XGetVisualInfo+0x2e) [0x7fb78db3d08e]
#4 /usr/lib/jvm/java-1.5.0-sun-1.5.0.16/jre/lib/amd64/xawt/libmawt.so [0x7fb78e0401f7]
#5 /usr/lib/jvm/java-1.5.0-sun-1.5.0.16/jre/lib/amd64/xawt/libmawt.so [0x7fb78e040431]
#6 /usr/lib/jvm/java-1.5.0-sun-1.5.0.16/jre/lib/amd64/xawt/libmawt.so [0x7fb78e041099]
#7 /usr/lib/jvm/java-1.5.0-sun-1.5.0.16/jre/lib/amd64/xawt/libmawt.so(Java_sun_awt_X11GraphicsEnvironment_ini tDisplay+0x9) [0x7fb78e0411c9]
#8 [0x7fb7b6360f7b]

Any help would be much appreciated!