Dear Iuri: I have tried with OpenACS 5.9.1:
a) start server
b) active developer support
c) activate TRN
d) restart the server
everything is fine (ds and TRN are turned off). neither turning ds on/off or TRN of/off reveal an error.
Probably you are using some old version. If the problem persists on your site, please submit a proper bug-report with version numbers on the bug tracker.