AEG ESPRESSO MACHINE

With the machine cold (or hot if you have the right implement and can keep your hands away from the steam) I would try to insert something like a pin or a small length of bicycle brake cable up the frother tube and see if you can free what probably is a plug of solid mik in the end of the frother. Sounds like a blockage, it may suddenly blast out steam if you free it and you have the valve open so watch out. If it's not that then I would take the valve apart, especially if the machine is making the right noises. I'm not farmiliar with AEG machines though.