Please help!

Up till this morning, all courier transfers have been working fine. Now I am getting the following error and it is preventing me from putting live some changes, which is a bit of a problem.

Any help would be most gratefully received!

System.Web.Services.Protocols.SoapException: System.Web.Services.Protocols.SoapException: Server was unable to process request. ---> NHibernate.TransactionException: Transaction not connected, or was disconnected
at NHibernate.Transaction.AdoTransaction.CheckNotZombied()
at NHibernate.Transaction.AdoTransaction.Rollback()
at Umbraco.Courier.Core.PersistenceManager.Rollback()
--- End of inner exception stack trace ---
at System.Web.Services.Protocols.SoapHttpClientProtocol.ReadResponse(SoapClientMessage message, WebResponse response, Stream responseStream, Boolean asyncCall)
at System.Web.Services.Protocols.SoapHttpClientProtocol.Invoke(String methodName, Object[] parameters)
at Umbraco.Courier.RepositoryProviders.CourierWebserviceRepositoryProvider.Rollback() in d:\TeamCity6\buildAgent\work\399aef48762b5884\Umbraco.Courier.RepositoryProviders\WebserviceProvider\CourierWebserviceRepositoryProvider.cs:line 372
at Umbraco.Courier.Core.ExtractionManager.ExtractRevisions()
at Umbraco.Courier.UI.Dialogs.CommitItem.TransferAndExtractOnSelectedRepo(String repo)
at Umbraco.Courier.UI.Dialogs.CommitItem.oneSteptransfer(Object sender, EventArgs e)
at System.Web.UI.WebControls.Button.RaisePostBackEvent(String eventArgument)
at System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint)