WordPress database error while editing/posting

Hello,
I have recently switched to WP 2.3 and until an hour ago or so it was working just fine. But just recently while editing a post/page or posting a new one, I get the following error:

WordPress database error: [Table ‘wp_wpdb.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

WordPress database error: [Table ‘wp_wpdb.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/content/l/a/e/laemo/html/wp-includes/wp-db.php:160) in /home/content/l/a/e/laemo/html/wp-includes/pluggable.php on line 391

The url of my website is: https://www.nmimsieee.com if you want to take a look. The post gets edited successfully, but I get this error instead of the page being redirected to the post/page list in the WP admin area.

Currently active plugins are:
Akismet
BBPress Integration
BBPress Latest Discussions
Dagon Design Form Mailer
Dagon Design Sitemap Generator
Democracy Polls
Full Text Feed
Get Custom Field Values
Google Sitemaps
Maintenance Mode
rc:custom_field_gui
Search Meter
Sidebar Login
Subscribe to Comments
Translate
Widgetize Anything
Wordpress.com Stats
Wordpress Database Backup

I have disabled suspicious plugins, but it’s of no use. It was working fine until an hour ago.. any idea what could be wrong?

Help would be appreciated. Thanks in advance!