what is the exact error message. Verbatim please. That looks like the kind of meaningless messages Microsoft is fond of using. What mail provider are you retrieving mail from. outlook.com perhaps? If the error message is the windows error that talks about a bad image then you will need to reinstall Thunderbird from getthunderbird.com as something went wrong with the update and one of the modified files did not get modified correctly. This sometime just happens, but more often is the result of anti virus processing. The reinstall should set you right with all your data and addresses remaining as they are not stored with the program. I normal reinstall will not be an issue. Using any sort of third party uninstaller program to remove all traces will usually cause loss of your data as well.