I noticed the latest WordPress upgrade was available on my server this weekend, it is really easy to get the latest version at Hostgator, my web host, with single click installation. So I installed version 2.3.1 of WordPress on all my sites and carried on blogging. But I started to run into some problems – every time I wrote a new blog post or saved a post I got an error message:

(WordPress database error: [Table 'xxxxxx_wrdp5.wp_post2cat' doesn't exist]
SELECT cat_ID AS ID, MAX(post_modified) AS last_mod FROM `wp_posts` p LEFT JOIN `wp_post2cat` pc ON p.ID = pc.post_id LEFT JOIN `wp_categories` c ON pc.category_id = c.cat_ID WHERE post_status = ‘publish’ GROUP BY cat_ID

Warning: Cannot modify header information – headers already sent by (output started at /home/xxxxxx/public_html/budget-travel/wp-includes/wp-db.php:160) in /home/xxxxxx/public_html/budget-travel/wp-includes/pluggable.php on line 391)

My posts were still being saved but this error message meant that I had to click on the ‘back’ key to check, and this slowed me down when writing or editing blog posts. Up till now I had not had any trouble using or installing the updates of WordPress, so I decided to find out if anyone else was having the same problems. Sure enough I found a thread on the subject of WordPress 2.3.1 error messages at the WordPress.org forum. Apparently the problem can be caused by plugins that are incompatible with the latest WordPress upgrade.

I was using the following plugins on my WordPress Blogs to improve search engine optimisation and site visibility:

• Adsense Injection
• Akismet – this is auto installed on my dashboard
• AllinOneSEO Pack 1.3.9
• FeedBurner FeedSmith 2.2
• Google XML Sitemaps 3.0.2.1
• Text Link Ads 3.0.6
• Ultimate Tag Warrior 1.3

Finding out which plugin was causing the trouble was really a process of elimination. The contributors to the forum discussion were not all using the same plugins as me, so this is how I decided to check: I just deactivated each plugin in turn to narrow down the list. I found two of the plugins were incompatible at the time – Allinone SEO Pack Plugin and the Google XML Sitemaps GeneratorPlugin. I visited the download sites of the plugin developers, and soon found they had developed updates that I could download and install. Problem sorted: I am still having problems with the TextLink Ads plugin, though, but that is another blog post.