Seems the cvs server was down when you tried it..
I just issued this at home:
And it worked fine. So try again and it should probably work.
cvs -d:pserver:firstname.lastname@example.org:/cvsroot/linuxdcpp login
On another note..
Sometimes ldcpp doesn't update the user list properly. A friend who had connection problems got diconnected a lot and reconnected every time.. After a long time ldcpp never showed him as online anymore. I had to restart ldcpp to get it to show him in the userlist.