Try to remove an entry and use the above one in place. But make sure that the numbers associated with the XSTR entries are the same as the ones of the entry you replace - just to be safe. I don't have a clue what those do, actually.
If that doesn't work, try working from a copied entry. Change things step-by-step until something doesn't work. Standard trouble-shooting procedure.

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"He who laughs last thinks slowest."
"Just becase you're paranoid doesn't mean they're not out to get you."
"To err is human; to really screw up you need a computer."
Creator of the
Sandvich Bar, the CapShip Turret Upgrade, the Complete FS2 Ship List and the System Backgrounds List (all available from the site)