How do I find the source of an error? I'm seeing the following error when running cron (in terminal via drush and on screen via the status report page.


  Error: Call to a member function getScriptTag() on a non-object in /home/loktah/public_html/includes/common.inc(1762) : eval()'d code, line 2


I'm not sure where to even start looking for the source. Any direction would be appreciated.
The line 1762 is inside drupal_eval(), in Drupal 6. You need to check  those nodes that use the PHP filter and call getScriptTag() on a variable that doesn't contain a PHP object.

It happens during cron tasks because one of the implementations of hook_cron() indirectly calls node_view() on some nodes.