I cut back my Drupal 5.21 installation as far as I could, deleting and uninstalling modules no longer in use, before updating to get things as trim as possible. I'm not even using a custom theme for my hobbyist site.
Imagine my surprise when my favorite CMS' upgrade from 5.21 to 6.15 throws all sorts of crazy errors. This happens if I just opt to have "system" upgrade itself, or other modules. The vast majority of the problems all live in "system".
I'm seeing several drop index failures, and most of those indexes don't exist at the end of the process. But a couple of them do exist despite the error. I initially ran with these errors and found to my horror that adding content was causing duplicate key violations and all sorts of terrible things, so I reverted back.
I'm also seeing some gallery-related menu_router inserts overrunning some values. Not sure what the devil is going on there.
Here's the error log in handy PDF format:
http://www.mediafire.com/file/uoq2d2zz2my/20100125_d5_to_d6_upgrade_fail...
I'm running PostgreSQL 8.4.2 on Fedora 11.
Any help is very greatly appreciated. I've reverted back to 5.21 for the time being, but I have a new Drupal 6 book I'd like to use so want to upgrade to stay current.