Help! Wikipedia server in dictionary unavailable

For the last few days, the Wikipedia lookup function in the Dictionary application has become unresponsive.

After a minute or two of the spinning thingie, I get the message that "Wikipedia server is currently unavailable." I've tried unchecking and rechecking Wikipedia in the Dictionary preference, deleting the Dictionary pref files, repairing permissions, etc., but to no avail. Is anyone having a similar problem? Any advice on how to resolve this?