Hey, I have had the same issue, got it for the first time when I installed 1.1.9 and then it went away again when I went back to 1.1.8, and now when updating to 1.2.0 it still happens. Going back to 1.1.8 it works fine though. Windows 10 64 bit here as well.
Tried deleting the client.prefs file now after updating again but still doesn't work. For me it does not stall on the downlords splash screen though, it just shows it for a second or two and then goes away. Same with the downlords-faf-client.exe process. Going back to 1.1.8 it works again.