This keeps coming up. People update their journal, put in an lj-cut, and then click on "view this entry" and get upset that the lj-cut didn't work. Perhaps it would be good to put a line in the FAQ about this? It would cut down on the support board issue somewhat.
Hm... Something like "If you wish to see your entry with the lj-cut after you have updated your journal, you will have to view your journal. If you go to "view entry", you will see the entry as it appears after clicking on the lj-cut. Additionally, the "preview entry" link will also take you to a view of your entry as it appears after you have clicked on the lj-cut. You will not be able to view your lj-cut when previewing your entry."
Except more professional sounding.
Edit: And maybe, just maybe, we can add that it's not possible to have the text under an lj-cut be a different security level from the rest of the entry. Have no idea how I'd say that, though....