We're having a similar issue after an upgrade as well. I've got a ticket open already.
[2014-11-05 1:44:23 AM]
Agent: N/A
Problem in Application_Start
The DELETE statement conflicted with the REFERENCE constraint "FK_st_TicketAttachments_st_Tickets". The conflict occurred in database "SmarterTrack", table "dbo.st_TicketAttachments", column 'TicketID'.
The statement has been terminated.
System.Data.SqlClient.SqlException (0x80131904): The DELETE statement conflicted with the REFERENCE constraint "FK_st_TicketAttachments_st_Tickets". The conflict occurred in database "SmarterTrack", table "dbo.st_TicketAttachments", column 'TicketID'.
The statement has been terminated.
at System.Data.SqlClient.SqlConnection.OnError(SqlException exception, Boolean breakConnection, Action`1 wrapCloseInAction)
at System.Data.SqlClient.TdsParser.ThrowExceptionAndWarning(TdsParserStateObject stateObj, Boolean callerHasConnectionLock, Boolean asyncClose)
at System.Data.SqlClient.TdsParser.TryRun(RunBehavior runBehavior, SqlCommand cmdHandler, SqlDataReader dataStream, BulkCopySimpleResultSet bulkCopyHandler, TdsParserStateObject stateObj, Boolean& dataReady)
at System.Data.SqlClient.SqlCommand.RunExecuteNonQueryTds(String methodName, Boolean async, Int32 timeout, Boolean asyncWrite)
at System.Data.SqlClient.SqlCommand.InternalExecuteNonQuery(TaskCompletionSource`1 completion, String methodName, Boolean sendToPipe, Int32 timeout, Boolean asyncWrite)
at System.Data.SqlClient.SqlCommand.ExecuteNonQuery()
at SmarterTrack.Data.SqlHelperInternal.ExecuteNonQuery(SqlConnection connection, CommandType commandType, String commandText, SqlParameter[] commandParameters)
at SmarterTrack.Data.DataLayerShortcut.ExecuteNonQuery(IDbConnection& conn, String query, SqlParameter[] parameters)
at SmarterTrack.Data.DataLayerShortcut.ExecuteNonQuery(String query, SqlParameter[] parameters)
at SmarterTrack.Data.DatabaseUpgrade.EnsureCommonObjectsLoaded()
at SmarterTrack.MRS.Global.RunStartupStep2()
ClientConnectionId:10ca4914-18b7-4f70-bba2-f3e1629acfcc