<------- does it look like a white version of my orange one there (which hasnt seen the light of day for a long time now)? I also have a white one. Umm firstly, citric acid and the aluminium boilers of the gaggias dont really mix. There are a few warnings aginst descaling with citric acid and baby Gs. So that could be your problemo with the milkyness. I wouldnt got drinking it in a hurry. If you wanted, taking off the boiler and checking out its guts isnt too much of an effort if you dont mind fiddling around. Thatll tell the real story anyway.
Actually, now you mention its white plastic, I think its the model after these which had the semi-clear red buttons right?