Michael Wood reported to OCAD Support that when saving an OCAD file from v11 to an earlier version, all text in the Map | Map Information | Notes panel is lost.
Solution (updated 1 Jun 2013)
Save v11 Map Notes to a text file and afetr saving as an earlier version copy into Map Notes.
Alternatively, if frequently editing earlier version files in v11 and saving back as earlier version, then keep Map Notes off line.
Patch to OCAD 11.
Result (updated 1 Jun 2013)
After further evidence from Michael, OCAD AG found the problem could be fixed. A patch will be in the next release of OCAD 11. Apparently no patch is required to OCAD 9.