>ip route 0.0.0.0 0.0.0.0 FA0
Don't use an ethernet interface as a default route. Always use the IP address of the next-hop that is directly connected to this interface. Causes all manner of ARP issues and traffic delays. Serial interface is OK because it is not a broadcast interface.
Reference
https://supportforums.cisco.com/message/3030916;jsessionid=7847BCECBB613537104BEC30C4D1669E.node0