I was just about to ask here whether the list server is down for everyone.
Thanks DJazz for providing this quick workaround. I had to replace HKEY_LOCAL_MACHINE with HKEY_CURRENT_USER to get it working. Now the game lists just one server called "Testing listserver". Is that how it's supposed to be?

EDIT: It seems to work. I can start a new game and it's shown in the server list.