Hi Marco,
I am having the very problem. I can debug any procedure on oracle 9.2.0.7, but on the other hand i can not debug on oracle 10.2.0.2. I had thought some privilege missing before i saw this post.
PL/SQL Developer
Version 7.0.3.1123 (MBCS)
Windows XP version 6,0 (build 2600) Service...