User getting access violation while typing in the Editor window. Usually happens after typing in the name of a table or other database object. User does not get the access violations when working in plan text style tab, only in SQL style and PL/SQL style tabs.
1. Turn off options for Syntax Highlighting in View | Toad Options | Editor | Display.
2. Continue using plan text style tab.
3. Reduce the number of database connections open.
4. Run only one instance of Toad at a time.
5. Uninstall Toad and install a new copy of Toad into its own new directory instead of on top of a pre-existing folder to avoid reusing an older or corrupted file.
Waiting for fix in a future release of Toad for Oracle.