There have been a couple of "additional language" help postings regarding the Zen Cart v1.5.4 issue identified by torvista ( Unfortunately, if a language-pack is installed before making the code changes suggested in that thread, it's a to get the issue corrected.

I suggest adding a HIGHLIGHTED sticky post in the "Addon Language Packs" thread, notifying potential language-pack users of the situation, with a link to the issue's description and solution.