I own an X1 and have had water/coffee spill through the top of the portafilter once. I cleaned all the gunk that built up on the gasket. I used a flat head screwdriver to scrap it off. I supposed as another post said, replace the gasket if it dried out, but I can't imagine why it would dry out. Keep the portafilter inserted on the group, even when you don't use it.
Always wipe off the edge of the portafilter basket before insert into the group head. This will help keep the gasket clean.
Pop out the portafilter basket and look through it towards light. Most, if not all of the little holes should allow light through them. If not, you can use coffee cleaner to clean the filter basket. Personally I just use hot soapy water and a scrub pad.
One final hint to keep from having to replace the element in the boiler. Always return the temperature back to coffee brew temp (~100 degrees C) after steaming milk. Run about 4 ounces of water through it to get the temperature down. It has nothing to do with water leaking but I learned the hard way after replacing the machine. :grin:
