Interesting choice of name for a machine. I had Giadia once in my travels and it wasnt nice. It certainly wouldnt make me go out and buy the namesake machine.
It sounds like your machine doesnt have a 3-way valve, but just a simple anti-drip valve. If this valve (usually just a ball, spring and seat) is jammed with scale or coffee crud, it wont seal properly and will leak. Another possibility is the spring may be corroded and lost much of its tension. Either way the machine will drip during heat up and not hold steam pressure. Thats my guess.
Actually its sunds like your machine may even have *a case of giadia... *;)
The usual way to fix this is to pull apart the group to access the valve. However, Im not familiar with your machine.