submitChnages throw zombiecheck

hi everyone,

I have a code similar to this, which performs a commit of a single row to a database table (SQL 2008)

using(var db = new MyDbDataContext(_dbConnectionString)){
    Action action = new Action();
    db.Actions.InsertOnSubmit(dbAction);
    db.SubmitChanges();}

Normally everything is fine, but once in a while I get the following exception:

System.InvalidOperationException: This SqlTransaction has completed; it is no longer usable.
at System.Data.SqlClient.SqlTransaction.ZombieCheck()
at System.Data.SqlClient.SqlTransaction.Rollback()
at System.Data.Linq.DataContext.SubmitChanges(ConflictMode failureMode)

There are a number of similar questions on SO but I after reading them I cannot work out the cause.

Could this be simply due to a SQL timeout (the exception occurs close to 30s after the call is made)?