When I try to upgrade Thunderbird I get an error that a previous upgrade needs to finish. I get an option to reboot the computer to allow it to finish. When I reboot nothing changes, I still get the same error. I tried to uninstall Thunderbird and I get the same error, i.e. a Thunderbird upgrade needs to finish. Reboot to allow it to finish. Gary Windows 7, 64 bit. using calendar linked to google calendar address book linked to google contacts.