Hi, I have started receiving this error on when trying to run a query:

2007-11-22 16:50:59,953 [(null)]-[5368]ERROR Mobux.Monitors.CustomerMonitor.Implementation() - System.ObjectDisposedException: Session was disposed of or closed
Object name: "ISession".
at NHibernate.Impl.SessionImpl.CheckIsOpen()
at NHibernate.Impl.SessionImpl.CreateQuery(String queryString)
at Mobux.DataAccess.PaymentTransactionDA.GetTransactionsByCustomer(Customer customer)
at Mobux.Monitors.CustomerMonitor.Implementation()

We are using Nhibernate 1.0.2.0. This query has not been touched and has worked for the last year without a problem, but in the last week we havent started receiving this error everytime we try to run the query on the live server. What would cause this to happen all of a sudden..?