I recently bought a new MBP with Lion installed. Having never used it, the new file system is a bit tricky to me.
My current problem: I have a JPG that I've copied from DropBox onto my desktop. I opened it in Preview, cropped, and tried to 'Duplicate'. It just says "The operation could not be completed". I then tried to "Save A Version", which gives me "The file XYZ could not be saved".
I copied and pasted the actual file as a different file name, to no avail. The same problem persists.
Command i on the file to get info. Make sure under "Genreal" that the file is not locked. Under Sharing and Permissions ensure that you have permission to Read & Write the file.
Yep! This info is often in the window title bar as well. The files I have opened in Preview usually include the term 'Locked' in grey at the top of the window. Once duplicated, the duplicate file is not locked and can be manipulated as expected.
1. open file in contained in your Dropbox using preview; it will be locked.
2. duplicate the file; it will not be locked.
3. close the original (locked) file.
4. manipulate the duplicate (not locked) file.
5. Save As what ever you want.