Lately my One Number feature seems to have stopped working.  My primary SIP registration works fine, but any attempt using "-1" or "-2" fails.

Some background info.

1. I've been a 2Talk user for more than 3 years
2. I've been using "One Number" for most of that time,  initially my config was TelecomNZ with 2 x LevelOne (German) phones,  
3. I changed over to Orcon Genius in September 2011 and continued using One Number successfully,    
4. I replaced the LevelOne voip phones with 2 x Thomson ST2030 voip phones about 6 months ago.
5. This problem surfaced about 10 days ago after working fine for 6 months.
6. I re-loaded the phone config file in case that was the culprit.
7. I disconnected both phones,  swapped the login details between the two and the "old secondary" phone became my primary SIP login and the "old primary" became my secondary SIP login using  xxx.xxxx-1.   The "new" primary one worked fine but the secondary would not register.
8. I have made no alterations to the Genius Modem/Router config other than the initial setup in September 2011.

SO,  I believe I've eliminated any issue with the phone hardware, phone config or my config of the Genius modem/router.

My only thought is that maybe Orcon have altered something either at their end or by remotely updating (sic) my modem/router....

Anyone got any ideas ???