I connect to my sip server via an ipsec tunnel, which takes care of any NAT and/or STUN issues. With the e51s i don't have any trouble using the voip service at all times and am only limited to the battery life. I configured the e52 with the SIP_VoIP_Settings app to successfully register a SERVICE with the asterisk, but it keeps loosing it's registration and doesn't auto-connect even though i've setup "always on" under my profile.
Do u have any clues regarding CONSTANT registration. I see there're new settings covering Presence(SIMPLE), VCC and XDM, but i don't comprehend their use yet.