I have a Plone 4.3 site that was a migration from a Plone 2.5 site. It had been working fine, but for some reason the default editor that shows up when editing any page or c
4.3 suffers from some random failures loading generic setup profile steps on creating a plone site. There are a few alternative ways to resolve this:
1) Identify the missed steps (in this case TinyMCE) and go to portal_setup and run them. Or, rerun all the steps.
2) Remove or comment out the line "PYTHONHASHSEED random" in base.cfg. Rerun buildout. Restart. Re-add your Plone site.
3) Upgrade to Plone 4.3.1. I haven't heard of anyone having this problem with 4.3.1. If you do, be sure to file a bug report!
Plone also stores the chosen editor in the user preferences.
Check http://yoursite/@@personal-preferences
There's a small script which migrates all users to tinymce -> http://plone.org/products/tinymce/documentation/how-to/how-to-set-tinymce-as-default-editor-for-current-users/