I followed directions on this page, and it fixed it for Firefox, but I still can't get Internet Explorer to come up. (Yes, I know it's old, but it still works best for some pages on my XP computer, and I like it.) I can see the process launch in Task Manager, but the window doesn't come up.
I did the repair and clean re-installation, I have tried disabling all add-ons in IE, turning off Avast's Web Shield, but nothing works. It won't even work if I completely uninstall Avast, and I could not do a System Restore. It will open in Safe Mode.
I am using Avast Free on an XP computer, with Firefox 52.0.2 ESR, and IE 8. Please help, as I really do need IE for some things.