Ctrl+F not working

[Thomas Blasejewicz]

Good evening
Ubuntu 12.04 / new clean install / English localization

The other day I noticed, that the keyboard shortcut "Ctrl + F" = search
is not working.
Let's say I open my home folder.
Press Ctrl+F --> nothing happens
Click: Go -> Search for files (Ctrl+F) = a small window opens allowing
me to search.

Just for the fun of it I tried to assign a keyboard shortcut -> Ctrl+F.
I get the error message, that this IS ALREADY assigned to "search for files"

If that is so, why is it not working??

Thank you.