User has a very large package body, over 20,000 lines, either in the Schema Browser or saved to a file. If the user highlights the code and copies it then paste it into the Editor, Toad 9.5 will hang. Toad 8.6.1 and QSR.EXE is able to post the paste immediately.
Install a copy of Toad 8.6.1 into another directory. Use this for very large code until a fix is released.
Use the Quest Script Runner found in your Toad installation directory as QSR.EXE. Pasting large code works in QSR. You can edit and execute it as you would in Toad.
When loading from the Schema Browser, double click on the package or try right mouse clicking on it and selecting "Load in Editor" instead of copying and pasting.
Waiting for fix in a future release of Toad for Oracle.