Unity 5 - Asset store window stays black - Unity (not responding)

Hi, I installed Unity 5.0 Personal Edition on a 64bit Windows 8.1. It seems impossible to get the Asset Store Window opened and working. When I try, I get a black window with the Asset Store tab on top...and Unity is seens as "Not responding" by Windows. I already tried to untick the DirectX 11 checkbox from the Player Settings. I also tried launching Unity as Administrator. I uninstalled Unity 5.0 and the former Unity 4.6.2 setups, cleaned the registry and the AppData folders then reinstalled Unity... Is there anyone else having that issue? Is there a workaround? Should I wait for an update? Thanks in advance for your feedback. Ulric