@diyer I wouldn't normally suggest using the Administrator account, though on XP that was possible.

You should be able to restore the bookmarks easily enough, some other files (logins and cookies) are encrypted to your user account and it is possible with a reinstall that your account has actually changed. Check in Help > About Opera to verify that your profile is where you think it is (as I say, it may have changed). If it has changed, then be selective about what files you put back.

There have been updates to certificates and security protocols since 36 was last updated. See if you can find a trustworthy source for updated certificates. Though come to think of it, make sure your date is set properly as an incorrect date will also cause certificate errors.