Agree with that last question. If it is cracking when you pull it up, just make sure you are pulling the material up as close to where it is nailed as possible. Start from one end of the molding, not the center. But depending how it was attached, some cracking might still occur.
Are you using a compressor and nail gun to install? If so, what gauge? I use 18 gauge nails to install thin, fragile moldings such as quarter round. sometimes, especially for stain grade, we use a 23 gauge pin nail with construction adhesive. almost non-existant hole to fill after too. Of course, this requires a 23 gauge gun...
If you are hand nailing, do what the other poster said and predrill. alternatively, to save some time, you can try blunting the tip of the nail a bit, then driving it.
Make sure you counter-sink all your nails so you can fill the holes in nicely