Thunderbird is stuck on mnimize

Does the toolbar show a '-' & '+' sign (along w/ an 'x')? Try minimizing to task bar, then R click Tb icon, then 'Restore'. Under Menu (3 bars icon) > View > Layout, try "Classic." Do you have any theme / Tb UI modifications, e.g. using a /chrome/userChrome.css file, etc? (try disabling - rename it, adding ".bak" to end of name); restart Tbird. Other addons installed? Try disabling them. Try 1 or 2 other Tbird themes (one of included in Tb installation). Menu > Tools > Addons Themes. Should be a few shipped w/ Tbird. If don't work, could try creating a new profile. To test, have to copy over data for at least 1 of your accts to new profile.