I don't know why, but I know it happening.
After realizing that both Fn+F1 and Super+S switches between workspaces, I used
xev and found out that Ubuntu senses Fn+F1 as Super+S.
In other words, Fn+F1 is interpreted as the same keystroke.
Why is this, and how do I fix it?
- The Leopard shortcuts menu has neither Fn+F1 nor Super+S
- When I bind a shortcut to Fn+F1, the workspace selection screen appears, and when I back out, I find it to be set to Super+S.
Turns out that my computer's bios reset whether I needed to use the Fn key to activate special keys, and now after fixing it I need to press Fn+F1, which is shown on my keyboard to be the Search key.