When you try to open a raw what does it do?
Most of the problems with raw is two ACR files in same folder, or ACR in wrong folder. Perhaps LR and PH are both putting ACR in folder?
I am on mac osx 10.7.4.
Your ACR should be in /Library/Application Support/Adobe/Plug-ins/CSx/File Formats/
There should be only one file there.
In PS (Windows) if you go to Help/about plug ins/camera raw it will tell you what version. In a Mac believe there is another route, something like Photoshop.
Adobe Raw Plugin stands in that folder. Nothing else...
I had this exact same problem, but with PS 5 & LR 4.1; then with PS 6, ACR 7.1 the same damn thing happens! I've uninstalled PS 6, can't afford it anyway. Tried using Adobe's DNG convert, the files "convert" to .DNG but they wouldn't open either. So darn frustrating as the whole system worked fine 2 days ago and now freezes while trying to open anything but a JPG! No changes to computer; MacBook Pro (unibody) 17", 8 GB RAM, 10.6.8.
I went back to 10.6.8, PS 5, ACR 6.7 (my D4 is covered) and reset prefs for both PS & LR and now things are working again.... time to reformat this darn thing and clean it up, what a pain!
BTW, do you or Curt know of a backup program that keeps track of serial #'s?? Having to find all those again will be a pain.
Alan, if you registered your software, your serials are available on your profile on the adobe site: Log-in , then click on "My Adobe", then "My products".