Ran a full system and boot time scan with Avast, as I do each month, without any previous problems. On the next boot, unable to access Firefox from desktop shortcut, toolbar or start menu. Firefox will not launch in Normal or Safe Mode. Unable to uninstall Firefox in Normal or Safe Mode. Ran ComboFix and Rkill and had no effect. Attempts to open Internet Explorer show "Cannot Display Web Page" message. Chrome not installed. Mozilla Thunderbird is installed and operates normally. Periodic Avast updates are received.
My understanding is that REVO Uninstaller will remove Firefox and that a "Clean" reinstall of Firefox will resolve this issue, but how can Firefox be reinstalled without a operational browser?