Has anyone ever come across this:
Fatal error: require_once() [function.require]: Failed opening required '/home/helenejulien/public_html/sites/all/modules/flag/includes/flag/flag_flag.inc' (include_path='.:/usr/lib/php:/usr/local/lib/php') in /home/sitename/public_html/includes/bootstrap.inc on line 3175
I removed the flag module from the sites/all/modules folder and removed it in the systems db table. Still can't get past it. Tried all kinds of variations - different versions, only changing the status on the rows in the systems table, etc.
Does anyone have a suggestion I could try? The only alternative I can see is to recover the site from a backup and have to redo 3 hours of work.
I am so discouraged by the amount of exceptions and errors I've had.... I can't be the only person who's had this experience. I'd love to hear what others have done to survive upgrades.

Comments
Oh... this sounds so
Oh... this sounds so familiar, but I didn't keep very good notes during my upgrade.
I have some recollection of having to use this during my upgrade at one point:
https://www.drupal.org/project/registry_rebuild
Maybe it will resolve your problem? Worth a shot I'd think...
Do you use drush? If so get
Do you use drush? If so get the drush registry rebuild plugin. Use the command drush rr that it provides. Could be related to the registry settings in the db which drush clear caches doesn't touch unfortunately in d6
it could be a dependency of
it could be a dependency of another module (or code in theme template, maybe) that is using Flag.inc. if so, you may need to re-write and re-include those function in flag.inc into some other site module..
look for module_load_include() functions
I do not know how you are
I do not know how you are upgrading, but try disabling the module, then upgrade, then enable it again.
If you move modules from one folder to another, for it to work 99% of the time you have to disable it, move it, then re-enable.
And if you do this you will also find any modules that depend on Flag will have to be disabled too.
Thank you all! I will try
Thank you all! I will try the suggestions.
FYI update
The registry rebuild worked like a charm. And this process cured me from using dev versions forever more..... Thank you so much for your help!
The site still has a lot of kinks to work out but everything is installed without any update.php errors or status report errors. I feel like I won the lottery!