I’ve spent a solid week reading through all of the posts concerning failed upgrades to 1.4.0. I have the luxury of having a development environment that I could trash and not worry too much about. I had a mirror of my production site loaded on the development environment. The steps I followed to get the update to work were:
Back up your config.xml (at the very least, your database (structure and data)) Delete all of the files in magento/var/cache
Download the full 1.4.0 archive and expand it over the 188.8.131.52 version replacing all of the files in the magento directory. chmod everything in your root (magento directory) to 777. chown all of the files and directories to the user and group your web server runs as.
You should be able to log into the admin interface at this point. Go to Configuration->Magento Connect. Click the Check For Updates button. The entire installation will turn biege with the 1.4 versions noted. Scroll down to the Mage_Core_Modules item and select the upgrade to it. Make sure Clear all sessions after successfull install or upgrade is checked, hold your breath and click on Commit Changes. You should see more than just the Core Modules download and update. This step is also making quite a few changes to your database. I ended up with 301 tables after this step.
Click on Return to Admin. Once back in the admin panel, go back to the Magento Connect page. Click check for Updates. At this point you should see that you have the majority of 1.4.0 installed. ***Note: you DO NOT want to update the default\blue frontend template. Doing so will cause any 1.3ish templates you have loaded to look pretty funky. Repeat the Check for updates, select an update, run it, return to admin, go back to Magento Connect until you see that you have everything other than the default\blue frontend template updated.
I’ve run several test transactions through the system, changed a user’s password, sent a newletter, added more items, created new categories and ran reports. All seems Ok… An iteresting item that I saw that is new is the Widget item in the CMS menu. I got real excited thinking that I may have a way to create menu\sub menu items on the front end other than category related items (like the URL to a second, third, fourth store)… No such luck.
I hope this helps some poor sole that has found themselves becoming “Konan the Librarian” with this upgrade.