Perhaps this topic applies? The symptoms are slightly different, but my guess is that it has the same cause.
Note that if you are using PL/SQL Developer 6.0.x, you can add this package to the "NEVER add debug debug info for objects" list on the debugger preference page. This way you can omit debug info for individual packages instead of all packages.
Okay, this is an Oracle bug, not PL/SQL Developer. I spent hundreds of hours on this issue. It has to do with the underlying object count coming out of the LINDA (aka, ADA) based language that PL/SQL is based on. Marco is correct in that you have the "Compile with Debug" switch set to true. You can recreate this bug in SQL-Plus by