Fatal error: Cannot redeclare ...

Pretty sad. Third time I spent a significant amount of time trying to get a 2.* site going. Third time I've experienced a completed "hosed" site.

*** I'd love some advice on how I might fix this. I realize that no one can repeat this situation as there are just too many variables, but I wonder if someone can make a suggestion based on the error messages below.

This is Not my normal Drupal experience, I assure you. I have successfully built several sites with Drupal Commons 1.* including http://ischoolnet.org.

Here's what happened:

I successfully installed 2.2 and got further than with 2.0 and 2.1, but now after installing many modules, I am getting "Cannot redeclear" errors when I do almost anything including adding or editing a node.
The last module I worked on was the error reporting configuration (/admin/settings/error-reporting).
I successfully installed ubercart, invoices, fb_social. Nothing really frightening. Now I get a version of the "Cannot redeclare" error even when I try to go to /admin/build/modules. Drush fails when I try to do anything:

Here are the errors I get from the Web site:
Changed Error reporting and then tried to add a new page for "Page not found."

***Went to node/add/page and got the following error:

Fatal error: Cannot redeclare node_page_edit() (previously declared in /home/intknow/domains/intknowledge.com/public_html/modules/node/node.pages.inc:12) in /home/intknow/domains/intknowledge.com/public_html/sites/all/modules/drupal-6.22/modules/node/node.pages.inc on line 15

***Changed Error reporting (after installing login tobbogan a day before)
Fatal error: Cannot redeclare system_main_admin_page() (previously declared in /home/intknow/domains/intknowledge.com/public_html/modules/system/system.admin.inc:11) in /home/intknow/domains/intknowledge.com/public_html/sites/all/modules/drupal-6.22/modules/system/system.admin.inc on line 59

***Tried to use drush to disable logintobbogan: drush dis logintobbogan -- got this:

Fatal error: Cannot redeclare system_help() (previously declared in /home/intknow/domains/intknowledge.com/public_html/modules/system/system.module:46) in /home/intknow/domains/intknowledge.com/public_html/sites/all/modules/drupal-6.22/modules/system/system.module on line 105

***Noticed the theme was not enabled (happens every time the cache is cleared as is well known). Went to /admin/build/themes and got this error:

Fatal error: Cannot redeclare system_main_admin_page() (previously declared in /home/intknow/domains/intknowledge.com/public_html/modules/system/system.admin.inc:11) in /home/intknow/domains/intknowledge.com/public_html/sites/all/modules/drupal-6.22/modules/system/system.admin.inc on line 59

***Tried to edit a node:

Fatal error: Cannot redeclare node_page_edit() (previously declared in /home/intknow/domains/intknowledge.com/public_html/modules/node/node.pages.inc:12) in /home/intknow/domains/intknowledge.com/public_html/sites/all/modules/drupal-6.22/modules/node/node.pages.inc on line 15