Is it this page you are trying to access - https://www.mozilla.com/en-US/plugincheck/

I just checked it and the site loads OK. Try clearing the cache and try again, it may be loading the error message from the cache. For details see how to clear the cache.

Your above posted "More system details" list shows two Adobe Download Manager plugins that you do not need.

See Troubleshoot issues with plugins like Flash or Java to fix common Firefox problems

Thanks, TonyE! I just used CCleaner and defragged my HD within an inch of it's life, and I could have sworn cache was cleaned. I got the scan page loaded!

Cor-el, are you speaking of the newest version of Adobe Acrobat, and Adobe getPlusPlus? It appears it was my cache memory needing purged, because I got the plugin scan page open soon after I cleared it. getPlusPlus is a download app, isn't it? Why would I not need the newest version of Acrobat reader, btw?

Thanks, cor-el for your reply; I sometimes need all the help I can get!

I had a similar issue too, turns out I did not allow access to mozilla.com from my noscript extension

The problem is affecting all the computers on my network. I have one running XP, one running Windows 7, and one running Ubuntu linux. The only thing in common is the use of Hughes satellite for the internet access. I can't see how this would cause a problem, because it should be transparent the user. I tried clearing the cache, but that didn't help. I was successfully able to check plugins this morning on a work computer using a different ISP. Has anyone else experienced this problem?

I too had to tell noscript to allow mozilla.org. It was a new computer and I guess on the older one I've taken all settings for granted and now I have to think about them on the new one. Not exactly the same situation (plugin page works then doesn't) but it may help someone who's added noscript;remember to tell it all mozilla is safe.

This problem has been occurring for the past two months. I have updated Firefox to version 3.6.16...including Flash Player to version 10.2.153.1 as instructed. I am able to click on the "Add-ons" tab and "find updates" for "Get Add-ons" and "Extensions." However, the "find updates" tab is not working for "Plugins." I followed one of your suggestions in your "troubleshooting plugins" topic (disabling the plugins...then enabling them after a check). That didn't work either. In fact, a message box would appear saying that Firefox has "disabled Flash" instead, which of course it did not, since I was able to confirm that the Flash Player update version was still intact. Unfortunately, it appears that updating the Flash Player through Firefox is not a standalone operation. Apparently it will not work properly unless a separate update is subsequently processed through Internet Explorer as well.

This problem continues in FF 6.0.2. Does not seem to be a real solution. No Script allows mozilla.com. No firewalls. Can't understand this one at all.

Checked everything I can. May have to uninstall FF and start over.

Crazy.