We have a small client with a 50 that recently started losing sync with the IP phones. It started about a week ago when they came in that morning and the phones were all locked trying to connect to the host. They rebooted the system and the phones connected right away. It started happening twice a day at almost the same time. It took them a week to call us. We went out yesterday and the phones were stuck trying to connect when we arrived. We connected to the system through the network no problem. The network switch and power supply are fine. They only have IP stations so we connected a digital phone and it functioned fine. We rebooted the system and the phones connected. We thought it might be power related so we replaced the power supply and the ups and started monitoring the power receptacle. After an hour or so of monitoring ( no problems) we left. We were gone about 10 minutes and it happened again. The system has 6 IP phones, 1 analog, and ESIs SIP trunks. Any ideas/suggestions before we hang another cabinet and swap the SIP licenses?