In Toad for Oracle's Schema Browser, my Tables list is empty

In the Schema Browser window of Toad for Oracle 9.7, the list of tables at the left is always empty, though I know the database still has tables. This happens whether I use the Dropdown, Tabbed, or Tree view. In Dropdown view, the top menu is the name of my database, and the menu below it says "Tables". But the list of tables is empty, and says "Cnt: 0" at the bottom.

The tables are missing from the Object Palette, too. But I can view the list of Triggers and other such objects fine. And importantly, all SQL queries in the Editor work and can access all tables. I can see the missing table names with SELECT * FROM all_tables and the column names with SELECT * FROM cols. That is no replacement for the Schema Browser, though, as it does not let me conveniently browse and edit the tables.

This problem just happened one day. I don't remember doing anything to cause this; all I did was browse tables and run SELECT queries like I normally do.

You might have a filter applied to your list of tables.

To clear a filter, change your Schema Browser view to Dropdown (using the second button from the right on the Schema Browser toolbar). Click the Filter Tables button with the gray funnel icon on the LHS's toolbar. This will open a window "Browser Filter for: [your database]". Click the Clear button in the top right, click Yes, and then click OK.