Mission Control custom key shortcuts not sticking
In 10.7.5, there's two ways to set custom key shortcuts for Mission Control actions (the one I'm interested in is the "Show Desktop" shortcut). I previously had "Show Desktop" set to ⌘ + (Space), and it worked. I just switched to a new mac (same OS, same model), and when trying to bind the key combo again, it did not work. I've been able to get a service that will produce the same effect bound to the same key, but when I change it to the Mission Control one, the effect does not take. It does not take on subsequent boots or reboots, either. I've also tried disabling my hot corners to no avail.
MacBook Air, Mac OS X (10.7.5)