wrong ange-ftp username

[Sven]

Dear list,

emacs ftp mode uses a wrong user name, so I can't login to my ftp server. E.G.

C-x C-f
/username@host:filename

emacs uses "username@host" as username, which is wrong, because username is 
"username" and not "username@host". I also tried ange-ftp-set-account to 
specify the ftp account, but emacs always tries to login with "username@host", 
which always fails.

Any ideas?
Thanks, Sven