Typing certain key combination on the keyboard gave me unexpected result in Toad. For example when I typed capital 'S,' it does a select-all.
You might have set a short cut key.
1. Go to 'View | Options'
2. Select 'Toolbars/Menus | Shortcuts'
3. On the right side, under the column 'Command' look for the action in question, like 'Select All'
4. Highlight it
5. Click on the 'Reset Current' button and it will revert back to the default short cut