As Colin mentioned, it will be worth opening a TAC case to troubleshoot this issue.
Meanwhile I wanted to draw your attentione to the some of the Androide related issues found by Princeton. I am not sure whether it is completely related to the issue you are describing or not, but I would say worth going throught this link once. :)
Link:
http://www.net.princeton.edu/android/android-stops-renewing-lease-keeps-using-IP-address-11236.html
Summary of the Android related issues found at Princeton :
Issue 1
After the lease has expired, the device continues using the IP address.
That is, it continues to respond to ARP Requests, claiming to own that IP address. It responds to ICMP Echo Request for that IP address. It responds to UDP and TCP traffic sent to that IP address. It initiates traffic to the Internet from that IP address.
Issue 2
Sometimes the malfunctioning device exhibits this issue in addition to issue #1.
While the device is continuing to use the IP address after the lease has expired, sometimes it unicasts DHCPREQUEST packets to the DHCP server for that lease, asking to renew the lease. It may do this for a few minutes, or for hours.
Issue 3
Sometimes, the device continues (or resumes) using the IP address from the old expired lease as well. That is, the device is now using both IP addresses simultaneously. (It answers IP ARP Request packets for both IP addresses.)