As anyone experienced this problem:
Im running POE for Cisco 504G phones with a PC attached to the LAN switch port on the phone. DHCP is being served through a Cisco 1800 series router.
It seems that the interface will shutdown and come right back on at DHCP renewal obviously resetting the phone and causing the PC client to disconnect. The only reason I noticed this is because it is right at the same time the lease is expiring. Both the phone and the PC are on the same VLAN.