bleroy (11/28/2012)
Have a look in the windows event log (http://support.microsoft.com/kb/308427), a number of categories there, check them all out (although Application log should be the most relevant), the right panel will give a list of events - sometimes a little cryptic, but generally using a combination of event time + related application would allow you to identify the relevant event (if any!) - simply scroll through the lists and check out the details related to the event of interest.
I get an error when attempting to expand the SQL Server Logs node in SSMSE:
Failed to retrieve data for this request. (Microsoft.SqlServer.Management.Sdk.Sfc)
An exception occurred while executing a Transact-SQL statement or batch.
(Microsoft.SqlServer.ConnectionInfo)
Also have a look at the SQL server event logs themselves,
**** from http://www.informit.com/guides/content.aspx?g=sqlserver&seqNum=242 by Buck Woody ****
the Error Logs in SQL Server are actually text files. They are normally found at:
Program Files\Microsoft SQL Server\MSSQL.n\MSSQL\LOG\ERRORLOG and ERRORLOG.n
Just checked that - there is absolutely nothing from the period yesterday evening when I was testing and experiencing those lockouts. There are some failed login attempts from several hours earlier, when I was messing with something else, and an automatic full backup task about 30 minutes later, but nada from the time period in question.