Like many people, I’ve had problems installing org-mode using elpa, resulting in the well known error
Invalid function: org-with-silent-modifications
This is usually due to not following the installation instructions:
When installing from ELPA, please do so from a fresh Emacs session where no org function has been called.
I’ve encountered this problem a few times on Windows installations, each time through forgetting the above advice. The solution was straightforward, go to (home)/emacs.d/elpa and delete the org file, temporarily rename the .emacs file so that you’re restarting Emacs to a completely fresh session (or start a fresh emacs without any customization with
emacs -q -thanks to iNecas). After that org-mode installs without a hitch.
And then I tried to do the same on Linux. Same error, same attempted solution. This time it didn’t work. I wasted half on hour on this until I tried a complete reboot of the PC. This time it worked. The lesson is, when it says fresh Emacs session, it means a completely fresh Emacs session.