Upgrading never works fine for me. The FAQ about upgrading to the next version from Cubecart is very unhelpfull. Don't try that method, the upgrade will not go successfull.
When I want to upgrade from the upgrade-message in the backend of the shop, I get the alert I have to do it by FTP because of permission-issues. These are the steps I take:
I backup the database
I backup the FTP.
I download the newest version from cubecart.com.
I delete the FTP (because overwriting isn't working because of permissions), except the folders modules/plugins, the images/logos, images/source, skins. In the Cubecart FAQ it says to overwrite everything, but don't do that! You lose you skin, images, modules en logo.
I upload the newest Cubart-files, except the folders mentioned above.
I run the setup, change the permissions as noticed, and fill in the preferences.
The shop is ready, but I have these problems always: the Global settings are gone, and need to be filled in again (pain in the ass, because I can't remember everything), the copyright in the footer is gone and needs to be created again (if you can remember that too). The Documents are in duplicate, I have to delete the new ones.
With the latest upgrade to version 5.1.2, a lot of images where seperated from the products, and needed to combine again.
Always a lot of problems and no easy FAQ or manual from Cubecart. Very disappointing...