I had the same problem with my widget manager a while back after uninstalling a top poster widget type, here is what I did to fix my problem, I am not running the CMS in my website, so I can't recall the exact steps I took, but this is a post I made at that time. It seems to be a problem with the CMS not uninstalling the widgets completely.
https://vborg.vbsupport.ru/showpost....9&postcount=48