Yes, my username is my SIP number, then @proxy01.sipphone.com
What do you have as an outcoming proxy? proxy01.sipphone.com or fwd.pulver.com?
I can connect to my account only if I have proxy01 as my outgoing proxy, even though IPKall shows fwd.pulver.com as a proper proxy for my account.
Again, I've got busy signal when I call my IPKall number from a landline.
I use proxy01 for STUN too. That's the only way it can connect to the network.