An IP phone must not be set to CFwdAll to a destination that results in a loop situation. For example, Phone A forwards to Phone B, Phone B forwards to Phone C, and Phone C forwards back to Phone A. Cisco CallManager has a Max Forwards Hops to DN service parameter, with a default value of 12, in order to detect loop conditions and drop the call. In order to change this default value, go to the Cisco CallManager administration page, and choose Service > Service Parameters, scroll down to Clusterwide Parameters and choose Feature > Forward > Max Forwards Hops to DN.
Also, restart the DBL component on all of the servers from Start > Program Files > Admin Tools > Component Services > Expand Component Services > Computer > My Computer > Com + Applications. Right-click the DBL and choose Shutdown and then Start.