Updated from 60.9.0 using the "help > about mozilla thunderbird" menu choice. 68 came back up with blank screens, no account information, etc. All data files, profile, are in place. Accessing the same menu shows "applying update" cycling in place of the update button. Allowed it to run for several minutes but seems hung. Tried a variety of steps, manually killing the process, rebooting computer, turned off security software, the only addon was lightning, uninstalled that. Downloaded clean 68.1.0 file from Mozilla and re-installed from scratch. Tbird still comes up with a blank screen. update menu still hung on "applying update" even after the manual download and install. Reinstalled version 60.9.0 and Tbird came up cleanly with all settings, folders, mail, addresses as usual. Seeing the numbers of other 68 complaints I assume we have a defective version in 68.1.0.