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I do recall an issue another user had several months ago, which meant that any time a phrase was used, some similar problem arose - I think this was something to do with something his hosting provider had installed, and was not XOOPS related.
I haven't had any luck finding the relevent thread however, as I'm very sure the poster did get this resolved in the end...
Have you tried installing a copy of your XOOPS site locally with XAMP (or similar) and seeing if the issue arrises?