Are you absolutely certain your LCD address calculations are correct? You have not said which LCD you are using, but some 4-line displays are configured as two 2-line displays, each with a separate controller. If that's the case for your display, perhaps you are selecting both at once. You might add some long long delay while outputting characters so that you could see if, when outputting the 'i' in "ijk", the 'i' appears on lines 1 and 3 simultaneously.