When you use acrylic stamps with solid images sometimes you have problems when they are new getting a good image. I've tried many ways to fix this and the one I use most often is stamp clean stamp and clean again. The following blog entry though gives you a good review of some other methods to use.
Notice she recommends the foam mat - ever wondered what that foam was for in CTMH stamps well thats your answer. I though as many of you know keep the large foam mats on hand - plus remember the CTMH self healing mat has foam on the back just for this reason.
Anyways here's the link to the blog -Preparing stamps blog