Many of my images are disappearing when I try to convert them. I had this same problem last year, but I would just replace the picture (which was a huge pain because there are 24 images per page) and then eventually after a few attempts they would all show up. Any ideas what the problem is?
OS = Operating System for your computer (and the version of the operatiing system, please, like Windows 7 x-64 or Mac OS X 10.8.3).
Patch level is which updates you have installed for your version of ID. CS6 is version 8, and the latest patch is 8.0.1. If you don't know, once you tell us the OS we can tell you how to find out.
Preview mode is accessed from a button at the bottom of the Toolbox, from the View menu, or by pressing W when the text tool is not active. It makes the pasteboard disappear, along with non-printing objects.