Hi Ian,
I have also been having the same problems for some time.
I am using Voipfone and my ISP is Virgin (I believe service is NTL based) through ADSL, BT provided line.
Always seems to be about the same time early in the morning, most odd. My router is the sip aware intertex IX66. I have 5 sip phones, Snom 360,2xSnom 220 and 2 Siemens optipoint
400's. During the week I have tried each phone individually, siemens optipoint 400, snom 360, snom 220,each shows the same problem. I have changed the registration time on the phones to 60 seconds as suggested by Voipfone, the log from the phone (snom 360) and (snom 220) seems to show it responds every 30 seconds!! , I have also changed various settings in the Router to no avail. It seems most odd, the other morning I made a call to Voipfone echo test 152 at 07.00 and even though the Router's log showed a problem the call connected perfectly, not tried incoming call yet during the problem in the log. Every morning the log from the Router shows a problem around, 6.30 through to 7.30!! No matter what phone is coupled up, the more phones connected the more errors. Yesterday the Routers log showed a similar problem during the afternoon but for a much shorter time span. During the day the log from the Intertex IX66 is near perfect, with maybe the odd registration error at most. I also tried registering the phone the other night with sipgate; it only showed a rejected state once during the night and early morning. Going back to when I used a Draytek router and a linksys router a couple of months ago, some mornings the phone showed Password on the display, just pressing cancel cleared the message. This has also happened on the Intertex router so am assuming there was a registration error similar to the ones I am still experiencing. This one has really got me baffled!! I have reset the router completely several times during the week rebooted the phones etc,etc, and seems to make no difference! To be honest it's not a major problem and the phones still work when I need them but its rather intriguing why the problem occurs.With regard to your side issue, I also have this, and was advised some time ago this was normal behaviour for the SIP traces, snipped reply below...
The unauthorised messages are part of SIP - they are normal. You try to register with no password, you get a unauthorised message with some authentication keys. Then the phone md5 sums together these keys with the password, and registers again. In this way, your password is encrypted so that it can only be checked by the server that sent the request - you could not reply the encrypted
password later. That is the very simple explanation.
Hopefully some one will come up with an answer, any thoughts most welcome. All the best John