Hi Janice,
As your machine has not been used for a while, have you checked the sponge bar? Perhaps the needles are sitting just a bit too high for the yarn to catch the comb. The other way of casting on would be to pull forward alternate needles, knit one row and hang the comb on the loops formed. Then bring forward the in between needles and continue knitting.
Hope you get it sorted,
Sue
September 2012