Hello,

This is the field notice:

http://www.cisco.com/en/US/products/sw/voicesw/ps4625/products_field_notice09186a00807e9632.shtml

In short: check router configuration and upgrade phone firmware!

One more thing to try, go into the telephony-service command and type 'create cnf-files' to rebuild the internal xml config files for the phones, this will ensure the time settings are same for all handsets, then do a reset all to make all handsets re-register and sync up their time. It is best to use an external NTP server for the system time, here is a config snip from a working CME that may help -

telephony-service

time-zone 48 <--- Sydney, Australia time zone

ntp server 213.157.226.100 <--- public NTP server