Which Leaf back is it? Do you have an example of such a .mos file that you could post (e.g., via YouSendIt)?
Eric, the model of the back is: Aptus 17.
We are up in Rocky Mountains with a rather slow Internet connection. A file is 17 megabytes in size and would take a long time to upload.
Is it necessary?
Make sure you have the latest version of Camera Raw.
I am able to open and process Leaf Aptus 17 files with CR 4.5 on my MacBook with OS X 10.5.4 and Photoshop CS3.
We have exactly the same versions installed. Can you outline what procedures you followed in opening these RAW files?
Did you set any specific preferences?
Go to About Plug-in in the Photoshop menu and make sure that you do have in fact ACR 4.5 correctly installed. There should be only one instance of ACR showing up there and it should be 4.5.
It sounds like there may be duplicate versions of ACR in that system and/or the Cache has not been purged through the Tools menu in Bridge for each folder containing the images, one by one. DO NOT use the broken global Purge Cache command in Bridge Preferences, as the cache will not rebuild properly after using it.
It's been over a year since the last posting on this thread, so I assume the poster has resolved the problem. However, for others - like myself - who are searching to the answer for this problem...
ACR only supports the uncompressed files created by Leaf backs - not the files created with lossless compression. Set the back to create uncompressed files and you should be fine.