Hello. I went to Tools, Plug-ins and check for updates as I do once a week, every week, and yet now, after checking, Firefox says 'no plug-ins detected'. My plug-ins are still all there in Tools, Add-ons, so why am I getting this message?

I check my plug-is for updates once a week, yet as of today, despite the fact that my plug-ins are all still there in Tools, plug-ins, after I click on the find updates button, I get the usual screen that tells me Firefox is checking for updates to my plug-ins, but then I get the message saying 'No plug-ins detected.' This has never happened before and it means I can't check for updates to my plug-ins.