The mud.org domain is nonfunctional, thus LambdaMOO is unreachable except by direct IP address (which is 69.17.114.80) until this is repaired. Some bureaucratic screwup; the owner of mud.org states it is paid up until 2007, but of course bureaucracies don't work on weekends. Hopefully tomorrow it'll be taken care of.
Update (wrog): In the meantime you can use lambdamoo.fyigm.com