I'm a silver surfer beginner giving Ubuntu a go on my backup PC because my Windows 10 drive has packed in. Everything is fine until I try to update from v 14 to v 15 or other installed software. These download OK but when I click 'install' I'm asked to authenticate with a password. I enter my administrator password and click authenticate, this fails and loops back to request a password. Frustrated to say the least. Regards WilRog.