Core issue
This issue is documented in Cisco bug ID CSCsf17256.
The event happens 10 seconds after a WebVPN connection.
Resolution
In order to resolve this issue, upgrade the ASA to software version 7.2(2), 7.2(1.25) or 7.3(0.108).
In order to download the latest version, go to the Software Download Page or open a TAC case.