Which cast on are you using when you run into trouble? It might be that switching to a different one could help.
Also, are your stitches really tight when you cast on? I have found that if I cast on too tightly, my stitches sometimes start to "spiral". If you have trouble with casting on too tightly there are a couple of things you might want to try:
Cast on with a needle one or two sizes larger than the needles you are going to do the project with
Put your two needles together (with the ends lined up and the points lined up), and cast on around both of them. When you are ready to knit, pull out one of the needles and you'll have a loose cast-on.
When I was learning to knit, I found that learning to cast on evenly was harder than knitting and purling evenly. It takes a lot of practice, and you'll get better at it with time. You can do it!