Why can't I delete Dropbox from my Mac?
Completely Uninstall Dropbox from Mac OS X
Reinstalling the latest version of the Dropbox can fix the uninstall process: Open Activity Monitor. This utility is usually located in the “Applications” folder, under “Utilities”. In the Activity Monitor, look for lines that say “Dropbox.” Click a line that says “Dropbox.” Click the X to force quit the process.