I was syncing some files from my PC to my Mac with Dropbox, but they never arrived at my Mac. I got a Cant Sync File(s): Permission Denied error. Heres how I fixed it.
Whip open Terminal.app.
Write these lines in, one at a time, return key in-between.
Notes: Replace ~/Dropbox with your location of Dropbox folder if you have moved it from default location.