Thanks, folks. I got it solved. I supplied PDF files to my commercial printer, using their PDF job options. Converted from IDCS6 to Press PDF. The original files I generated looked perfect on my monitor. They did whatever it is they do, probably ran it through their RIP and sent me *their* PDF proofs. My original InDesign file had a lot of transparency, line drawings in the background, etc. They said their PDFs matched mine exactly at their end, but they sure didn't on my end. At any rate, the did a little more research and gave me the correct fix. In Acrobat Preferences, under Page Display, they told me to UNcheck "Smooth line Art". Apparently, that does some anti-aliasing or something, and was responsible for screwing up the display of my files. With that unchecked, everything was back to normal and looked good. Just thought I'd explain it in case anybody else has weird results like this. I guess their RIP made some subtle changes that somehow affected the display of the files with that checkbox turned on. So, no need to reinstall at this time. Lou