Hi John. My name is***** you for your question and the opportunity to assist. Do a refresh of Firefox
to see if it clears this up. At the top of the Firefox page click Help and select Troubleshooting Information.
(if you don't see Help at the top, right-click the 3-horizontal-bar icon in the upper right corner and select Menu Bar)
On the Troubleshooting Information page click Refresh Firefox (twice)
When Firefox reopens check if the computer still locks up.
Does the computer lock up like you describe if you're using Internet Explorer or Chrome?