Preview corrupted? - shows checkerboard pattern on PDFs

I'm using an iMac OS 10.6.8 & Preview version is 5.0.3. A few weeks ago I started getting this translucent grey checkerboard pattern across many PDF documents opening in Preview. It doesn't happen with all PDFs, and in some documents any photos on the page show clear while the text areas are covered with the checkerboard pattern. If I print the documents, there is no checkerboard pattern on the document. When I open the same documents on my old MacBook Pro running Preview 3.0.9(?) the documents are all checkerboard-free.

I'm thinking my Preview app is corrupted somehow. Do I have to delete Preview and re-load from my OS DVD? If so, how do I delete Preview?

Thanks in advance for your help...

Do you have your original Snow Leopard install DVD? You'll need to make sure that you can extract a new copy of Preview from it before removing the old one from your computer. Preview is an application along with others that are in your applications folder. But, you don't want to remove it unless you're able to replace it with a new copy.