I just started having this problem today, so it happened shortly after applying an OS X update (from Apple) ostensibly for battery improvements on my MacBook Pro.
Repairing disk permissions and rebooting did not help.
TCP/IP properties, of course, never changed (and besides, it worked before today).
Clues welcome. I obviously can't roll back the battery improvement patch! It's also possible that the patch is a red herring and something else is amiss. Don't know what though ...
[UPDATE - A THIRD REBOOT of the MacBook pro and now all's well. Will keep an eye on it, but nothing else was changed other than the reboot.]
Last edited: Apr 28, 2007