I don't know if I can help, but I have a couple suggestions.
Make sure you're always cabling on a "right side" row. On the Irish Hiking scarf all the stitches in the actual cable will be knit stitches. There are purl stitches that border the cable, but no purl stitches on the right side of the actual cable. When you slip your stitches onto the cable needle, make sure you slip as if to purl - both when you slip onto and off of the cable needle. Otherwise you'll be twisting the stitch (and if you slip knitwise both on and off, you'll be twisting twice) and that will both tighten up those stitches so it will be hard to knit into them, and could make them appear purled on the right side.
One way to do cables that might be easier for you, at least at first, is to rearrange the stitches first, then knit them.
For example, slide 3 stitches purlwise onto cable needle and let hang in back (or front depending which way you want the cable to cross) of work.
Slip next three stitches from left to right needle purlwise.
Slide the three stitches from the cable needle back onto the left needle without twisting them (the leftmost stitch on the cable needle will be the first stitch you slip back to the left needle).
Slip the three stitches you put on the right needle back on the left.
Now you have six stitches on the left needle that have been "crossed".
Knit all six stitches from the left needle to the right in the normal manner.
I hope this helps!