PP, I think you may be doing the ribbing wrong if you are getting bumps where you are not changing over from K to P and ViceVersa. are you going under the needles when you change which side the wool is on? are you knitting from the front of the stitch at all times? Knit goes through from left to right, purl goes right to left, with the needle you are kitting from on the left at all times. I might take some pics to show you if it doesnt make sense. Let me know if you need to see it.