1. Switching between maximized and normal screen size, the scroll bar disappears, even though there is more data than shown.
2. When opening a table in the Schema Browser, switching to an Editor window, and then switching back to the Schema Browser, the scroll bar to the right appears to be missing.
Most problems disappear when undocking the MDI (Multiple Document Interface) child by clicking the inner "restore window" button and then clicking maximize on the MDI child.
Issue fixed in Toad for Oracle 9.7.2. The latest version of Toad for Oracle can be downloaded here.