What you and Technodad post looks suspiciously like you might not be aware that there are two different keyboard shortcuts to be defined, one for clipping, and one for quick entry. The quick entry one is in the General preferences tab, and it brings up an empty Quick Entry window (which looks exactly like Technodad's "if I use the keyboard shortcut" case). The clipping one is in the Clipping preferences tab. I suggest you try setting the Quick Entry one to control-option-space, and the Clipping one to cmd-shift-, both of which are known to work, and the clipping shortcut in particular makes a nice pair with the OmniOutliner clipping shortcut which is on the adjacent key. Once you have things working, you can try changing one of the shortcuts at a time if you want a different shortcut for one or both of the functions.