Thunderbird upgraded automatically to 38.0.1, with some initial issues with incompatible Lightning, as commented elsewhere, but they were automatically fixed. But now I have a problem that the main window is displaced down by one white line, but Thunderbird acts as if it were OK, producing the effect of a miscalibrated mouse pointer. A message window, on the other hand, shows a black one line on the bottom, and exhibits similar behaviour. Similar things happen with other windows (e.g. password manager one). If I restart it in safe mode (all addons disabled), everything is fine. If I manually disable all addons and restart, then it shows the extra lines as usual. Wierd.

Any help would be greatly appreciated. Regards