asterisk users - May 2006 - problem with sip registration ramdomly

Hi all

          I have setup sips accounts to an asterisk server from a
provider, I know that there are using asterisk real time for sip users
definitions.

         Sometimes  in a ramdom basis I receive:

                       chan_sip.c:9596 handle_response_register:
Forbidden - wrong password on authentication for REGISTER ....

         And i cannot make or receive calls.


  Nothing has change in configurations file, and if I make reload
chan_sip.so, everything goes right again.  I have set up in sip.conf
following parameters:

                   registertimeout=50
                   registerattempts=0

but it seems that there is no effect.

Could it be due to database interacction.

Thanks