I recently had an issue with file associations over Nautilus, in my Gnome desktop.
After installing the Dropbox client for Linux, I tried the "Launch Dropbox Website" and it opened Gedit with some HTML code inside (with a text editor instead of the browser !!! ).
Then I realized that when I try to open an HTML file, the application that opens it to me is Gedit.
- If you use "right button / open with" option and you check the box "Remember this application ...", It seems not work.
- You need to use "right button / properties" and in the tab "open with", set the appropriate application, for instance firefox
After this, the option in Dropbox worked.