Running under X11/Motif, LispWorks may print a message saying that it is unable to connect to the X server. Check that the server is running, and that the machine the image is running on is authorized to connect to it. (See the manual entry for command
xhost(1)
.)
On Mac OS X, if you attempt to start the LispWorks X11/Motif GUI in Terminal.app, an error message
Failed to open display NIL
is printed. Instead, run LispWorks in X11.app.