I have a an issue with one particular VPN user. They are using the built in Windows Vista client to connect to my ASA 5510. All other users do not have an issue and i receive the following error at roughly the same time of day when the drop happens. Authentication is done by my AD Server which handles all logins.
<177>%ASA-1-713900: Group = DefaultRAGroup, Username = username, IP = x.x.x.x, construct_ipsec_delete(): No SPI to identify Phase 2 SA!