But of course all cookies have been deleted, so I have to login to websites again.įirefox is up-to-date (84.0.1, 64-bit) and running on Windows 10 Enterprise.

Luckily I use Sync, so my many bookmarks are backed up. When I relaunched Firefox, I got the above error message. The existing window was fine, so I closed that but had to kill Firefox in Task Manager. The new window showed my homepage (blank tab) but was unresponsive: I couldn't type into the address bar, click a bookmark, or even close the window. I haven't yet spotted a pattern, but the most recent time it happened, I had the browser already open and either opened a new window or clicked Firefox in my start menu. To protect your information, create a new profile for this installation of Firefox.'

Using an older version of Firefox can corrupt bookmarks and browsing history already saved to an existing Firefox profile. 'You've launched an older version of Firefox. Over the past week I've had this error popup a few times when Firefox is launched:

Find older versions of firefox