I don't recall anything being changed in 1.3.x related to htmlarea.
The message that "HTMLarea is undefined" is a javascript error, largely related to your browser being unable to load or process the javascript code needed to run the htmlarea components.
Check your server's errorlog to see if it's getting requests to files that don't exist....
Do you have any firewall software on your PC? if so, turn it off for testing.
Do you have a .htaccess file in the root of your store folder that might be blocking access to the htmlarea folder?
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