It really depends on what you eat. I had been experiencing post-meal spikes following the initial "good" numbers 2-3 hours after eating, but 4-5 hours later and I was in the mid-300's. A meal that is high in protein or fat is digested slower than a meal with lower protein/fat levels.
Take a pizza (or pieces thereof) for example. The fats in the cheese are going to be digested slower than the carbs from the bread. The response about the square wave bolus is the correct course of action on this matter. The normal bolus will take care of the carb factor while setting the square wave to deliver X units of insulin over a period of 3-4 hours will definitely reduce, if not remove, the post-meal spikes.
Mind you the square wave can only be done if you're using an insulin pump. If you are relying solely on injections, I would say try changing what you're eating (to lower fat/protein content foods) in order to see if that makes the spiking happen less frequently.
Hope that helps :o)