In openSUSE 10.3, ImageJ with Java 1.6 can give an “Assertion `c→xlib.lock' failed.” error that prevents it running.
Open the file /etc/profile in your favourite text editor as the root user.
Then, add the the following statement just before the end of the file:
# # Enable lock assertion workaround # export LIBXCB_ALLOW_SLOPPY_LOCK=true