Brian,

Yes that correct. Sometimes Tomato suddenly send wrong messages to the sip server ... that causes authentication fails. We suspect the password strip off some characters. This is happen suddenly and after some time it will work back normal.

I try with 1.25 , 1.27 and 1.28  ..... no luck then I switch to dd-wrt all problems go away. I am using 

Firmware: DD-WRT v24-sp2 (08/07/10) voip

what is the Tomato firmware u r using?

Thanks

Lloyd