Can you try to delete application data which resides in C:\Users\<username>\AppData\Roaming\SQL Developer\system220.127.116.11.80 and do not migrate setting when start the SQL Developer?
SQL Developer QA Team
It was a total clean installation and not a emigration from a previous installation
1) New PC with Windows 7 64 bits
2) New JDK 1.7 64 bits installation (with the JRE standalone option installed)
3) Download the new SQL Developer 4 and extracted it
4) At the first run, it ask me for the JDK location and browse to it
5) It also ask for to upgrade from a previous installation, but any previous file location was displayed at the window.
Try Window > Reset Windows to Factory Settings
Thanks very much, It's working !