Did you try search in safe mode ? This will identify the problematic things running in firefox. [ [Mode] ]

This thread helps you in the case when pointer spinning continiously http://mzl.la/1BAQAMz

ydmstr said

I cannot check for add on updates. the little arrow jus keeps spinning. tried refreshing firefox and no help. any ideas.

I get this.....When I go to "Tools" then click on "Add-Ons" then click "Plug-Ins" and then click on "Check To see If Plug-Ins Are Up To Date" it goes to Mozilla Check Your Plug in Page all it does is sit and spin at the Checking with Mozilla on the status of your plugins. I am using Win7 Pro and just downloaded Firefox update to 35.0

I just ran the plugin updater, no problem.

Start Firefox in Safe Mode {web Link} by holding down the <Shift (Mac Options) > key, and then starting Firefox. Is the problem still there?

Go to the web page. Once the page is loading, mouse to the address bar and Left click the icon. A window for displaying site information should come up. Select More Information. Now select Permissions. In the menu, find the plugins, and set all of them to Allow. This action will only effect that one site.

FredMcD said

I just ran the plugin updater, no problem. Start Firefox in Safe Mode {web Link} by holding down the <Shift (Mac Options) > key, and then starting Firefox. Is the problem still there?

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Go to the web page. Once the page is loading, mouse to the address bar and Left click the icon. A window for displaying site information should come up. Select More Information. Now select Permissions. In the menu, find the plugins, and set all of them to Allow. This action will only effect that one site.

I also think if you go to this Forum link this will help as well

https://support.mozilla.org/en-US/questions/1041556