Issues with updating modules on Drupal 7 I have a Drupal 7 website that I upgraded from Drupal 6 awhile ago. I am trying to upgrade some of the modules that have had updates since then, but I am having issues doing so. When I click the "Continue" button on the "ready to update" screen, I receive the following unformatted text on a blank white background:


  Installing updates
  
  Status message
  
  Operating in maintenance mode.Go online.


The url of the page is example.com/authorize.php?batch=1&amp;op=start&amp;id=4206

I checked the error logs in Drupal, and there are a few errors reports:


  Notice: Undefined variable: finished in _batch_process() (line 344 of
  /home/mysite/public_html/includes/batch.inc).
  
  Notice: Undefined variable: old_set in _batch_process() (line 339 of
  /home/mysite/public_html/includes/batch.inc).
  
  Notice: Undefinedvariable: old_set in _batch_process() (line 338 of
  /home/mysite/public_html/includes/batch.inc).
  
  Notice: Undefined
  variable: old_set in _batch_process() (line 337 of
  /home/mysite/public_html/includes/batch.inc).
  
  Notice: Undefined index:
  init_message in _batch_progress_page_js() (line 136 of
  /home/mysite/public_html/includes/batch.inc).
  
  Notice: Undefined index:
  error_message in _batch_progress_page_js() (line 135 of
  /home/mysite/public_html/includes/batch.inc).
  
  Notice: Undefined index:
  title in _batch_progress_page_js() (line 127 of
  /home/mysite/public_html/includes/batch.inc).


Any ideas on what might be causing this and how I an fix it?
I have encounted this in the past and usually you get a module that causes an issue with AJAX. 

What I would suggest is to update modules manually (download from drupal.org, extract and upload then run update.php) or via drush one by one. 

If you are doing multiple modules at once this can happen quite often. 

Also make sure you have Overlay module disabled as for some odd reason this can cause the same error. 

Your best bet is to update modules one by one to isolate which module is causing the issue.