volgens Tim Hunt.
No, you just need to make sure that when you copy the Moodle code to your server (This bit of the upgrade instructions http://docs.moodle.org/25/en/Upgrading#Install_the_new_Moodle_software) that you have copied all the files. If any files get missed in the copy, or get corrupted, then Moodle will not work.
It's one advantage of using git to manage the Moodle code. The git status command will verify that all the files are what they should be. If you are not using that, then you probably need to use a file comparison program to verify the files.