My "f" key won't work within Directory Opus with I want to search for a file. Every other key on my keyboard works including the "F" key. The "f" key works on every other program I use. Any idea as to why it doesn't work and how can I fix it?
Do you have that key assigned to act as the searching key/shortcut? It's not the standard.
You can check Prefs PAGE="quickkeys" to see, if it's listed there. Or at least under > customize > keys.
No, I have not assigned it.
Does the keypress trigger anything, or does nothing happen at all?
Either there's a hotkey on f within Opus (which will show up under Settings > Customize Toolbars and Keys > Keys) or something like AutoHotkey/AHK or the keyboard drivers are configured to change what the key does when Opus is active.
I am probably way off here but when x didn't work on my keyboard, I needed a new keyboard 
Always check trivial reasons
I checked all the setting. I don't see "f" anywhere. Should I remover Opus from my machine and reinstall it?
...david
Before you do that, you could try to assign the f key to some other function, for example Set METAPANE=Toggle to see, if that works.