It looks like lisp might have crashed and repl lost
connection to it. Try clicking Reconnect button on repl view.
However if lisp has crashed that might not be complete solution that
you are looking for.
Can you tell us more about your setup? What OS, Cusp, sbcl,
how did you install cusp? Also it would be helpful if you could
start eclipse from command prompt and send us log that is printed
there - this way we might be able to pinpoint the problem.