designer problem RME-00020: Internal API error - ORA-06502: PL/SQL: numeric or value error: character string buffer too small

Hello everybody,

I'm new to Oracle, come from a PostgreSQL /Python environment, and I'm
following a training in Oracle / Designer etc. (mostly self-study).

I have a problem in Designer. It seems that when it wants to store
information about diagrams I make a database error occurs. I found
this link
http://forums.oracle.com/forums/thread.jspa?threadID=284633&tstart=105
but there isn't any mention of a solution.

Does anyone know how to solve this, or how I can get access to Oracle
bugs? TIA!