i am having problems with Add-ons checking for updates. 

Hi i am having problems with Add-ons checking for updates. The first problem is that in add-on manager, even though i have it set to automatically update add-ons, it has no history of finding any and it's failure to find a new version of a plug-in meant pdfs weren't opening see full details here ... https://support.mozilla.com/en-US/questions/829011 The problem i am now having is that when i manually check for updates in Add-Ons manager, it pauses for a few seconds, and completes it's task by saying it hasn't found anything. If i then close Firefox, i can't open Firefox again until i go into task manager and kill the process. It says it's already running and i have to close it first?!