Mine was leaking at the plastic output fixture of the steam unit. It's the white one on top with a single (probably rusty) screw holding it into the heater. To check this (only if you know how to be safe, please), start the unit with the covers off and look for water or steam bubbling out along the joint between the plastic and the metal. To fix mine, I removed the existing screw, carefully drilled and tapped the hole and used a new fastener. It works just like it did when it was new.
Caffeine Addict, May 2009