I posted this question in my previous post, I hope I can get some helps.
I created a Photoshop Panel using Extension Builder 1.5, the panel is running perfectly in Window, but when I switch to Mac, things broken. I found the SDK on Mac is unable to get the Document.fullName when I open an image file in JPG/GIF/PNG formats, event with workaround solution provided from Bob (http://cookbooks.adobe.com/post_Creative_Suite_Extensions_and_the_Photoshop_CS5_Re-17727.h tml)
In fact, it is not Photoshop event issue, if open a JPG image from my Disk, click on a button in my panel that will get the activeDocument, then try to get the File object from it, the Document.fullName always null. However, if I open the image from Photoshop installed folder, it seems fine.
I took the project I included in my reply to your other thread, and modified it so that I could open a file, click a button, and see the contents of app.activeDocument in the debugger. I then opened a JPG, and debugged the extension in Photoshop.
No problems on this end.
It works fine after upgrade to Mac OS 10.6.7