Looks to me like your offsets are, well, off. The start offset of each 'array' should be the base address of previous 'array' plus it's size...
Code:
memtest1 = 0;
memtest2 = memtest1 + 3;
memtest3 = memtest2 + 6;
Does that do what you're expecting?
edit: DarkStar types faster than I do
