The debugging process is runs on the package, procedure, or function. But when the "Halt" Button is pressed, TOAD hangs. Toad also hangs when stepping through code and an unhandled exception occurs.
Check if there are any "after servererror on database" triggers. If one exists in the database, disable it.
If this kind of trigger does not exist, please refer to solution 1528.
Waiting for fix in a future release of Toad for Oracle.