[Jochen Witte]

After re-installing the bundle, I am not any longer able to assign a clippings shortcut. It simply doesn't use it. If I try to use an existing shortcut, Omnifocus complains (which is correct).

[Schalke04]

As many posters are saying: It's just a matter of assigning a new keyboard that isn't used by Mail.app already. However, it seems that there are not many combinations available after the latest update.

For me the following combinations are working:
shift+cmd+o
fn+ctrl+alt+cmd+o
fn+ctrl+alt+cmd+x

The last two look a bit complex, but I like them: I just press all the buttons left of the spacebar and the letter [o] or [x].

EDIT:
Just started using my external keyboard and noticed the bottom two solutions are not very good, because the fn button is not in the left bottom corner. I suggest using ctrl+alt+cmd+o (or x if you prefer).

[HERMAN]

I still have the keyboard shortcut to the Quick Entry (F13), but the Clipping trick (F14) is lost and there's no way to make OF re-register that one. Tried multiple things (uninstall/install the Mail Clip-o-tron), checking shortcuts in Sys Prefs...

I've tried other keystroke combinations - to no avail.

EDIT: I'd suggest that everyone also does a restart after following the guidelines in the sticky. That solved my problems: a complete system restart.

All systems functioning properly now.