We also have this problem. From reading the other answers I can gather that it is a stuck non return valve as the pump is running when the hot taps are on but no hot water coming out of either kitchen or bathroom taps. I have also replaced the micro switch which hasn't solved the problem. I hope this answer has helped further with this problem. My next question is, how do you replace a non return valve on the hot water cylinder!!!
Olivia and Joe, August 2010