Decided to upgrade designer (yes ! we’re still working with this tool…). First tested it by importing the owner (and in my case HSU65 from headstart, and a testuser) in another database…
Downloaded patch 10_2_r5. Unzipped, runInstaller, upgrade the client. No problem.
Started the RAU-utility for upgrading the repository, pushed the button ‘Upgrade’ and off we go… Box opens with an import, and it stays open / freezes with the following text:

import done in WE8MSWIN1252 character set and AL16UTF16 NCHAR character set
export client uses WE8ISO8859P1 character set (possible charset conversion)
. importing DES10G_OWNER objects into REPOS_OWNER
. . importing table “CK_INSTALLED_OBJECTS” 7800 rows imported
. . importing table “CK_PRODUCT_ELEMENTS” 545 rows imported

Waited for half an hour, but it hangs, no doubt about it. Closed the import box, and the process continues!
Upgrade repository o.k.
Then the test. Opening designer, delete an object and connection was lost with the database:
RME-02102: Not connected to a database
RME-02121: Failed to open cursor
RME-02124: Failed to execute SQL statement: select decode(the_tab.state, ‘I’, 0, ‘O’, 1, ‘N’, 2, -1) from i$sdd_object_versions the_tab , I$SDD_WA_CONTEXT CTXT WHERE CTXT.OBJECT_IVID = THE_TAB.IVID AND CTXT.WORKAREA_IRID = :WA AND CTXT.WASTEBASKET = ‘N’ AND THE_TAB.IRID = :IRID

Solved this by :
alter system set “_optimizer_cost_based_transformation”=off scope=both;

Let’s say this is the Oracle way…