Why can't I assign my keyboard shortcut for Clipit?

[starplanet]

I've got Clipit 1.42 keyboard shortcut installed.

The default keyboard shortcut is: CTRL ALT H

I want to change this to: CTRL '
(That's the CTRL key pressed this the apostrophe character.)
I'd also be OK with CTRL #
(CTRL + he hash key)

It doesn't like these hotkey assignments.

Is there a problem with my chosen hotkeys?
Or should I find another clipboard manager?

Thanks.