(Cross-posted to my journal and lojban)
On the Lojban mailing list, Pierre Abbat challenged people to find a sentence which means one thing in Lojban and another in Loglan; he had helpfully posted a list of false friends and other word pairs to the Lojban tiki.
John Cowan came up with this:
"le barda mi dakli" means "the big one is a bag with me in it" in Lojban, but in Loglan it means "the one who rewards is more likely than me".
Likewise, "gutra le maksi" means "A womb of the magnet!" in Lojban, "Be strange to the maximum value!" in Loglan.