When Mac users get a new computer, the easiest way to set up is with Migration Assistant. This works well, but it sets up a Mac OS account on the new computer which has the same username as the account on the old computer. If the old computer is still to be used, this means having two different accounts on a network that have the same username. It's not difficult to alter the username, but this leads to a problem on Dropbox, caused by permissions issues in Mac OS.
One of the hidden files in MacOS from Dropbox is /Users/username/.dropbox . Once the username has been changed to (eg) new_name, trying to access the Dropbox app in any way, even trying to uninstall and then re-install it, brings up a Dropbox message asking to change permissions for the Folder /Users/old_name/.dropbox . This can't work because that folder no longer exists.
I contacted Dropbox help, who were efficiently helpful in supplying a Terminal script that solved the problem -- but it took time for me to realise what was happening, and then a number of contacts with both Dropbox and Apple help.
I suspect an easy Dropbox workaround would be tricky. I suggest that an explicit warning should be included somewhere in the Dropbox documentation for Mac users intending to change their username.
