Multiple Errors - Beyond my Expertise

Greetings,

I am developing a website for an educational institution. I used CCK to create a simple, custom content type. But, as has been my experience, I am running into errors after starting to work with CCK.

The problem comes when I go to update the settings of pathauto and tell it to "bulk update node paths" and click "save configuration." I get the following error printed to my screen (just white screen with black text):

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Warning: Table 'watchdog' was not locked with LOCK TABLES query: INSERT INTO watchdog (uid, type, message, severity, link, location, referer, hostname, timestamp) VALUES (1, 'php', 'Duplicate entry 'pathauto_node_content_marketplace_listing_patter' for key 1\nquery: INSERT INTO variable (name, value) VALUES ('pathauto_node_content_marketplace_listing_pattern', 's:0:\\"\\";') in /home/drupalpublic/docs/includes/database.mysql.inc on line 120.', 2, '', 'http://portal.wls.wels.net/admin/settings/pathauto', 'http://portal.wls.wels.net/admin/settings/pathauto', '10.10.11.88', 1163512824) in /home/drupalpublic/docs/includes/database.mysql.inc on line 120
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What I do at this point is simply reload the page /admin/settings/pathauto (without re-sending form information) and my site is visible again and I get the following two errors printed in the message box:

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user warning: Duplicate entry 'pathauto_node_content_marketplace_listing_patter' for key 1 query: INSERT INTO variable (name, value) VALUES ('pathauto_node_content_marketplace_listing_pattern', 's:0:\"\";') in /home/drupalpublic/docs/includes/database.mysql.inc on line 120.

warning: Cannot modify header information - headers already sent by (output started at /home/drupalpublic/docs/includes/database.mysql.inc:120) in /home/drupalpublic/docs/includes/common.inc on line 266.
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My area of expertise is CSS and design, and working with Drupal without getting too in-depth with the code (I have very basic PHP skills). I have developed several Drupal sites, so I am by no means a newbie, I just don't know much about dealing with errors. As a result, I don't really know where to go with this error.

I would greatly appreciate it if someone could help point me into the right direction. While the site still works, I would like it to be working without errors before I launch it.

Thank you!