I discovered what was occasionating the Runtime Error on Windows 7 x64, when trying to execute the Boxee.
My username on Windows is "Sírio", with the accentuation on "i". The user directory created by Windows has the accentuation too. When trying to execute the Boxee using my user (windows logon User), it tries to create a c:\users\SÃ*rio\Appdata\Roaming\boxee directory, in lieu of c:\users\Sírio\Appdata\Roaming\boxee.
I tried to execute boxee from a user that don't have accentuation on the name and it worked normal!!