It can be a worn out pipe or gasket. It also can be a loose connection, untighten screw or even a broken screw.
Open the back pannel and try to spot where it leaks. Even if you did not just used it, there should be some marks, stains, mineral deposits or wet areas.
A flashlight will comes in handy.
Make sure that all pipes are undamaged, tight and securely fastened.
REPLACE any cracked, punctured or otherwise damaged pipe, whatever it's material.
If you atempt to plug/weld a hole in a metal pipe, it may just burst elsewhere...
Check at the junctions between metal parts. Make sure that there are no loose or missing screw.
You may need to replace a gasket or O ring.
If it's the PUMP thats leaks, unless you can find a replacement at a good price, it may be cheaper or beter to simply replace the whole machine.
Kuälinar, November 2011