the ef disappeared as an option

the message I got when this module stopped showing as a checkbox and attendant ui in the exposed filters settings of my view:
Notice: Undefined index: views_ef_fieldset in views_ef_fieldset_display_extender_plugin->options_validate() (line 255 of /var/www/wwwadmin/data/www/dontgotomysite.net/sites/all/modules/views_ef_fieldset/views/views_ef_fieldset_display_extender_plugin.inc).

I had been using it successfully to group filters (with better exposed filters, which still works). Not sure exactly when It broke by not showing up as an option (checked or not) in the settings of the exposed filter, but I think it was because i saved the view.

the message I got when trying to uninstall:
"PHP Fatal error: views_plugin_display::destroy(): The script tried to execute a method or access a property of an incomplete object. Please ensure that the class definition "views_ef_fieldset_display_extender_plugin" of the object you are trying to operate on was loaded _before_ unserialize() gets called or provide a __autoload() function to load the class definition in /var/www/wwwadmin/data/www/dontgotomysite.net/sites/all/modules/views/plugins/views_plugin_display.inc on line 272"

I am also getting this error after uninstalling and clearing the cache

And, fwiw this module is awesome. now I gotta go learn views templating instead.