Index: oup/current/DataAccess/Access_OniArchive.pas
===================================================================
--- oup/current/DataAccess/Access_OniArchive.pas	(revision 248)
+++ oup/current/DataAccess/Access_OniArchive.pas	(revision 252)
@@ -72,5 +72,5 @@
   end;
   FFileName := DatFilename;
-  Fdat_file := TFileStream.Create(FFileName, fmOpenRead);
+  Fdat_file := TFileStream.Create(FFileName, fmOpenReadWrite);
   Fdat_file.Read(Fdat_header, SizeOf(Fdat_header));
   header_pc  := True;