afni.nimh.nih.gov

What OS are you running? I'm not sure whether it would be
sufficient to kill afni, though it may be. I have seen that
once (in the main afni GUI), and I restarted the X server
(since it certainly appeared to be an X problem).

If killing afni's process does not help, restart the X server.
On a linux box, you can do that with ctrl-alt-backspace (not
delete). On a mac you might be able to just terminate the X
program.

- rick