mysteriously stopped working unless I use freetagging

I have been using this for a few weeks and it worked wonderfully, it's a great module. Today, however, all my taxonomies mysteriously reverted to the unwieldy scroll list. I installed two new modules: fixed datadropdown and module weight, both of which I have uninstalled. Any ideas why that would affect this?

And why would it work if I check "free tagging" but not if I don't. I do not want free tagging.

thanks.