So SIP works great. Send and receive calls. Fine. I go on about my day. Call comes in. I notice that it doesn't come into the n900. I take the call.

Shortly thereafter, I check asterisk ("sip show peers") ... hrm. Not registered.

So... I've been iterating. If I "edit" the sip account on the phone and hit "save" ... it immediately re-registers and everything works. I set the keep-alive interval down to 2 minutes (although my FreeBSD firewall is quite good --- whatever it takes).

But still. After some amount of time that I haven't precisely measured, SIP stops registering.

Has anyone taken a crack at this problem? My search-foo isn't good enough to tease this out of the board, here.