My settings:
Program Window - Background Compilation - UNCHECKED
Program Window - Safe Compilation - UNCHECKED
Connection - Session Mode - Dual Session
Connection - Oracle Home - emtpy (using default)
Connection - OCI Library - empty (using default)

btw: The package compiles successfully when executing it in Command windows

Marco, that issue seems to be introduced with the final release version. it wasn't there in Beta6. I get the error now with most (not all) of my packages and types.

Nothing relevant has changed between beta 6 and the final release. To ensure that it's not the database state, can you shutdown and restart the database instance?