read this: http://www.cisco.com/en/US/partner/products/hw/gatecont/ps514/products_administration_guide_chapter09186a00801e0e00.html#wp1062011bit 21

If the Voice VLAN is configured on your DHCP Server Port remove it. I had this Problem with new HP Server. The Server answered the DHCP request of the Phone in VVLAN with a Adddress from the Data VLAN.So the update failed.

You are not alone.Same with a 3725. We get the same Output.TAC said resolved with 12.2.15T2 but its all the same.Did you find a Solution for your 3640, as TAC says it only applies to the 3700 Routers.SS