Deleting the preferences file worked for me after everything else failed.
c:\Users<USERNAME>\AppData\Roaming\Arduino\preferences.txt (Windows Vista\Windows 7)
- Arduino failed to launch, waited a minute, launch 4j error appeared
- Disabled bluetooth (no WiFi installed)
- Uninstalled V1.0 and tried with previous version - same error
- Uninstalled Java, tried again
- Multiple javaw.exe appearing in processes
- Renamed / deleted the Arduino folder under
- Looked through the log to see where the program was hanging (no success)
- added EN to the profile (was empty before); can't even remember where I found that idea...
- Replaced rxtxSerial.dll file
... finally deleted the preferences file and all seems to be ok.