Problem linking to voip server

[Jdub]

I'm having a problem trying to get this to link to the voipuser.org server; I want to see if the whole thing improves my cheap and hence nasty USB phone box which works well with Skype but has very bad audio for SIP (using X-Lite).

 

Set Skype2sip with

 

username: justinwhite

server: voipuser.org (have tried sip.voipuser.org)

 

but whenever I start Uplink get:

server voipuser.org did not respond to register (sip:justinwhite@voipuser.org)

check server details for that line

 

Any ideas?