It's probably the hot water hose from the spigot to the tank. The thin plastic gets brittle from the constant heat. That's were mine was leaking. The hose is hard to replace unless you can get the exact shaped hose part.
Kevin
March 2009
Mine is doing the same thing. It looks like it is leaking at the base of where the bottle is put in.
If you take the bottle off and grab the base that the bottle sits in and turn it will come off. It has a rubber seal inside.
I am now looking for the replacement seal.
Kevin Mayes
December 2008
I have the same problem. Did you have yours fixed? If yes, care to share your experience?