If you have a Lion workstation connected to an AFP server volume, and work on Photoshop files directly off the server, there is a critical bug I’ve experienced that you should be aware of to avoid data loss.
While navigating the AFP volume, if you are using the Finder’s column view, and have the Photoshop file you are actively working on highlighted in the Finder (so it displays it’s preview in the far right column)… you will get an error in Photoshop when attempting to save stating “Could not save […] because write access was not granted”. After clicking OK to this error, the Photoshop file you were trying to save on the server will DISSAPPEAR! The file will remain open in Photoshop, and you will be able to save again to the server, but if you close the file without resaving the file will be completely lost.
This problem only occurs if you have the file highlighted in the Finder while in column view when attempting to save. If you are using list view you won’t experience it, nor will you experience it if you only occasionally have the file highlighted in column view (therefore it may seem like a random problem).
Work arounds include NOT using column view, and unchecking the Finder’s option for “Show preview column” (from the Finder click on View->Show View Options) which will prevent the preview from showing when files are highlighted in column view. A more advanced and use-at-your-own-risk work around is to disabled the launchd system agent named com.apple.quicklook.ui.helper, which will prevent the problem from occurring while allowing you to still see a limited preview in column view.
I have confirmed this problem occurs with both OS X 10.7.2 and 10.7.3 when connecting to a Lion server. According to a long thread on the Adobe Discussion boards, this same issue can manifest itself on different operating systems with different servers. So far I’ve only seen it with Lion workstations connected to a Lion server, see here for more info… http://forums.adobe.com/thread/732422