After upgrading to Hardy Herron some pretty critical Java applications stopped working – they all crashed with this error:

java: xcb_xlib.c:82: xcb_xlib_unlock: Assertion `c->xlib.lock' failed.

This particular application uses IBM JRE but the error is the same in Sun Java 6.

Apparently it’s a known problem in Java and the initial response is that it should be fixed in Java 7.

A workaround is to add the following line to ~/.profile:

export LIBXCB_ALLOW_SLOPPY_LOCK=true

Remember to log out and in to activate the change.