I don't think I've ever cooked a cake that comes out the way the recipes says it will.
I guess oven temperatures vary. But I agree with pastafreak, I always seem to have to cook cakes longer than the specified time in the recipe. So I'd add a little extra onto your cooking time and pop a circle of greaseproof over the top during the last part of cooking so that the top doesn't get burnt.
Good luck, remember, we all have these probs, you're not alone :-)