Thank you all for your responses. Apologies for the slow return, but the checking has taken time.
I tried to deactivate all plugins using the "select all" and "deactivate" but came up with a requirement to change the permissions setting of wp-content to 777. This I have done. I did try uninstalling one plugin at a time, first, but no category change.
I have deactivated plugins, switched to Twenty Eleven theme ( and back to Socrates), reloaded the wp-admin and wp-includes folder from a fresh download of wp3.3.1. No change
Unsure as to how I should reset the plugins folder - ???
I have created the required category using the Category link in the Dashboard column at the outset, and I still do not have any means of changing the post category.
There are 10 tags attached to the post
I am fresh out of ideas.
The post itself 'http://moneyproblemssolutions.org/wazzup-doc' has listing of Categories, but not the new one I want to use.
Appreciate your interest and help.