One point on the X11 driver: it sets a number of colors - currently 128 by default. This should be OK on a 256-color 8-bit system or better.
However it is creating private colors. As a result, if you are running IE, Netscape or some other color hungry applications, you may not have 128 colors available. This can cause libx to die. The best solution is to use fewer colors if you routinely keep netscape and other applications open on your screen and if you only have a limited number of total colors available.