Whenever it's time for you to upgrade modules on your site, you should have a checklist of the steps involved. One step I've recently added to my checklist is to clear the site cache just prior to uploading the updated module files.
I learned this lesson with a recent Views upgrade. While working on my dev server (#1 on my list!) I found that if I didn't clear the cache prior to installing the updated Views module, I was faced with the dreaded White Screen of Death (WSOD to those of us familiar with it). After a few minutes of my time in the Views issue queue, I found other people with a similar issue and the result was consistently some type of cache-clearing activity. Once I reinstalled the old versions, I cleared the cache, reinstalled the new versions and all was great.
For the record, here's my module upgrade checklist:
- Perform the upgrade first on a machine other than your live server
- Login as User 1
- Backup the database and files on your live server (I use the Backup and Migrate module for the database backup)
- Put site into maintenance mode (admin/settings/site-maintenance)
- Clear the cache (either from admin/settings/performance or via the Admin Menu.
- Delete the modules you're going to upgrade (don't just overwrite them with the new modules, delete them first).
- Upload the new modules
- Go to the admin/reports/update page to verify the new modules are installed
- Go to update.php and run any database updates
- Go to the admin/reports/status page to make sure you're all green-checkmark happy
- Test your site
- Take your site out of maintenance mode.
Did I miss anything? Do you have any additional steps in your module upgrade checklist?
That's not a problem I've ran into, but good info to have.
I keep all of my sites (and clients' sites) in SVN and have found that occasionally I have to remove all of the files from the local working copy before updating modules to catch files that are removed or renamed.