Problems with Cleantaste with EAM 3500

Hello everybody!
Thanks to your good advice we bought the EAM 3500 in January 2008 and are very satisfied since then.
We clean and care for it thoroughly, yesterday we cleaned the brewing group, milk container and accessories very thoroughly again. When I made myself a cappuccino afterwards, the Cleantaste started to spin. We already had the problem a few months ago, I mean that would have been immediately after an extremely thorough cleaning. But then it stopped on its own.
The following happens: The cappuccino can be optimally prepared. When you press the clean key, it first cleans briefly with water and then suddenly draws milk instead of water. Even if you get off the button, she keeps pulling milk and it doesn't stop. That's funny, isn't it? Does anyone have any idea what's the problem? We would be very grateful for help!

Love greetings Maike