Ok,
Does the Serial Monitor show up?
If you use Serial.begin() in your sketch Wiring will try to open the Serial Monitor.
If you want the COM port to be closed you should try to exit from that window as it should close the COM port.
I'm on Windows 8 x64 as well, and FT232RL based boards have worked fro me.
Maybe you could copy and paste the error messages you get?