I've had the same problem, but I managed to solve it by deleting the following file:
.technic/lastlogin
On windows, this is located in %APPDATA%/.technic/lastlogin
I can restart the launcher and it works. The only down-side is I have to re-enter my login details.
If I choose to "remember my password" then I have to do this EVERY time I want to start the launcher. If I don't select "remember" then it works every time.