To follow up on the date issue to hopefully help you with more info, I get dozens of these errors in the event log a day mostly from guests;
System.Data.SqlTypes.SqlTypeException: SqlDateTime overflow. Must be between 1/1/1753 12:00:00 AM and 12/31/9999 11:59:59 PM.
at System.Data.SqlTypes.SqlDateTime.FromTimeSpan(TimeSpan value)
at System.Data.SqlTypes.SqlDateTime.FromDateTime(DateTime value)
at System.Data.SqlClient.MetaType.FromDateTime(DateTime dateTime, Byte cb)
at System.Data.SqlClient.TdsParser.WriteValue(Object value, MetaType type, Byte scale, Int32 actualLength, Int32 encodingByteSize, Int32 offset, TdsParserStateObject stateObj)
at System.Data.SqlClient.TdsParser.TdsExecuteRPC(_SqlRPC[] rpcArray, Int32 timeout, Boolean inSchema, SqlNotificationRequest notificationRequest, TdsParserStateObject stateObj, Boolean isCommandProc)
at System.Data.SqlClient.SqlCommand.RunExecuteReaderTds(CommandBehavior cmdBehavior, RunBehavior runBehavior, Boolean returnStream, Boolean async)
at System.Data.SqlClient.SqlCommand.RunExecuteReader(CommandBehavior cmdBehavior, RunBehavior runBehavior, Boolean returnStream, String method, DbAsyncResult result)
at System.Data.SqlClient.SqlCommand.RunExecuteReader(CommandBehavior cmdBehavior, RunBehavior runBehavior, Boolean returnStream, String method)
at System.Data.SqlClient.SqlCommand.ExecuteReader(CommandBehavior behavior, String method)
at System.Data.SqlClient.SqlCommand.ExecuteDbDataReader(CommandBehavior behavior)
at System.Data.Common.DbCommand.System.Data.IDbCommand.ExecuteReader(CommandBehavior behavior)
at System.Data.Common.DbDataAdapter.FillInternal(DataSet dataset, DataTable[] datatables, Int32 startRecord, Int32 maxRecords, String srcTable, IDbCommand command, CommandBehavior behavior)
at System.Data.Common.DbDataAdapter.Fill(DataSet dataSet, Int32 startRecord, Int32 maxRecords, String srcTable, IDbCommand command, CommandBehavior behavior)
at System.Data.Common.DbDataAdapter.Fill(DataSet dataSet)
at YAF.Classes.Data.MsSqlDbAccess.GetDatasetBasic(IDbCommand cmd, Boolean transaction)
at YAF.Classes.Data.MsSqlDbAccess.GetData(IDbCommand cmd, Boolean transaction)
at YAF.Types.Interfaces.IDbAccessExtensions.GetData(IDbAccess dbAccess, IDbCommand cmd)
at YAF.Classes.Data.LegacyDb.message_findunread(Object topicID, Object messageId, Object lastRead, Object showDeleted, Object authorUserID)
at YAF.Pages.posts.GetFindMessageId(Boolean showDeleted, Int32 userId, Int32& messagePosition)