After upgrading from 2.9.2 to WordPress 3.0, alot of users have been getting the “Call to undefined function in taxomy” error. This is a simple fix. The reason for getting this error is b/c there are plugins that might be conflicting the upgrade, the best practice would be disable all plugins first before upgrade. If you already hit the upgrade button without disabling your plugins then you’ll have to ftp to the plugins folder, create a sub folder and name it anything, (eg. /inactiveplugins), copy all your plugins to this sub folder and try the site again. After everything is back working I would re copy and activate each plugin one at a time to find the problem plugin. Easy way to find the plugin problem.
Here’s a list of plugins so far that’s been doing this:
1)WP Ecommerce Shopping Cart Plugin
2)A Podcast Plugin (don’t remember the full name)
*Note : if you’re unable to do the upgrade due to memory issue, just disable the plugins first and try again.
Please leave a comment if you find this helpful.