Ad hoc network not shown

I am connected through a wireless network.

I want to setup a different wifi network (ad hoc) to connect my mobile phone.

I went to Knetworkmanager (systemtray icon). Add wifi, mode: ad-hoc, security wep (read somehwere that other encryption is not supported by networkmanager).

But it does not show up. Do I need to enable a server somewhere? Or does it not work if I am connected through wifi myself?

Thanks!