The usual suspects here are differences in the object ownership, the group membership, or maybe an access control list entry.
I almost never use the GUI for these cases. The GUI is cute. It's pretty. But it's just not as compact, nor as concise
Launch Terminal.app and issue the commands:
ls -ale@ ~
ls -ale@ ~/YourFilenameHere
and post the results.
This assumes the file is in your login directory. ~ is command-line syntax for your login directory, and the YourFilenameHere in the ~/YourFilenameHere specification should be replaced with the name of your file. The id command will show the details of your identity and your groups.
Yeah, I know. I'm referring to the command line as being less arcane and easier to use than the GUI. Ah, well.