I don´t know if you still have your phone bricked, but i had the same problem, and fix as follows:
I think the reason because the error appears is because when you connect your phone, Windows (mine is Windows 7, i don´t know if this explain the same trouble in Windows 8) aumatically find and install the driver. But the driver installed by windows don´t have the digital sign, so the port is not properly installed, although then digitally sign the port. It can be check in "Manage My Devices", if a yellow triangle appears in the port, then you have a big trouble, and you can not flash the phone.
How i fix it: When i connected my phone, close the windows search of driver immediatilly. With this simple step, windows did not install the driver without the digital sign. So, you can sign the port with the program posted in this thread. If everithing works, when you check in "Manage my Devices" you won´t see the yellow triangle in the port.
Now, you will can flash and unbrick your phone.
This is i solve that problem on my phone, i hope it works for yours!!.
Again, sorry for my english, i am from Chile, and still learning the language.