Tip - Good Question: Help! Why Do Cupcakes Always Get Stuck In These Silicone Muffin Cups?

I received some silicone muffin cups last year as a gift (the fluted stand-alone kind that look like a muffin tin liner). I've tried to make several batches of cupcakes in them and every time, not one of the cupcakes has slid out easily; they all break or stick to the sides. I've Googled this and rarely find any reviews or blogs where people have this problem. They all swear by silicone's non-stickiness, so I can't figure out what I'm doing wrong. Any thoughts? I've tried spraying with baking spray and not using any grease at all and it hasn't made a difference. Sad cupcake maker in Brooklyn, Liz (To All Good Questions)