[Freeswitch-users] 2009-09-02 15:21:44.665608 [CRIT] switch_time.c:454 Reverse Clock Skew Detected!

Hi there, Can anyone give any insight to this following message: 2009-09-02 15:21:44.665608 [CRIT] switch_time.c:454 Reverse Clock Skew Detected! This is on a WIN2003 machine with the last call hangup exactly 20 minutes and 20 seconds earlier. Just wondering how CRITICAL this really is? Many thanks Phillip Jones