Log into your broadvoice account. Click on the account tab. Click on "Manage MultiPresence". Go through the steps for a generic sip device.

Once you have done that, go back to the main account page by clicking on the account tab. There should be a pane call "My Devices", under that should be the sip device. Click "Show settings". On the N900 put <10 digit phone number>@sip.broadvoice.com in for account. Put in your Auth_password from the "show settings" page. Click on "advanced settings". Put in your 10 digit phone number for your user name. Note that the proxy name on the settings page of your broadvoice account is wrong, replace the '-' w/ a '.' and put that in as your outbound proxy on your N900. Save, look to see that it is enabled. Once enabled, on your way you go!