try this for Nokia E51…
* TOOLS > SETTINGS > CONNECTIONS > SIP SETTINGS
* Add a new profile called “Home”
* Service Profile: IETF
* Default Access Point: Your Home AP
* Public username: sip:202@192.168.4.69 (Replace with your extension number, and Asterisk IP address)
* Use compression: No
* Registration: Always on
* Use security: No