Maybe its the way you are holding the yarn, or if you turn your work the opposite way of the plies at the end of each row. I am not sure if that made sense. I have not had trouble with Simply soft, but I find some plied yarns do tend to unravel on me for above said reasons. Good Luck.
Mom to my bundle of energy, Logan 4-2-05
OTN- Cable front turtleneck for me
I am Chrissyb on ravelry!