I have recently migrated to KDE from unity (ubuntu 12.04). I have a PPPoE network where I live. Under unity, gnome, xfce I am able to set up a DSL connection and everything works fine. I tested a live cd opensuse (kde) and when I try to set up a DSL connection it fails in a weird way. Under kde (ubuntu) happens the same thing. I tested also an ZevenOS KDE and fails.
This is what I get when I try to set it up:

I am sure my username and password are correct. I set it to connect automatically and to be a system connection. Ethernet tab, IPv4 Address and IPv6 tabs are default. Under PPP tab only "Allow BSD compression", "Use TCP header compression" and "Send PPP echo packets" are checked. I also tried other combinations.
The weird thing is that if I log on with unity and make the connection it works. If I log back in with KDE I see the DSL connection created on unity and it works.