I have the same issue. No error messages, no response from the computer at all. The battery charges, but that's it. I've installed drivers, installed Samsung Kies, etc. When I open Kies, it says to connect a device, and I follow the instructions you mention above, click the "connect to Pc" button, plug in the cord, and nothing at all...
I've tried on two different computers, one is a desktop with WinXP SP3, and the other is a Win7 machine. No luck at all on either. Can you help?
The drivers that you installed, are they the current ones from Samsung (dated Feb of this year)? The one from Feb makes your phone a plug n play device, essentially.
Also, you can try Kies air on your phone. But it has to have access to a wireless device, like a laptop. If your tower is connected to the internet wirelessly, that works too.
That said, enable wireless internet on the phone, go to your apps on the phone and tap Kies air and press start. It'll open up and give you an ip to type into your browser. That's the wireless way to access your phone files.
When you connect your phone to PC via the cable, there's a finicky order to do it or it won't detect it by USB debugging.
Settings > wireless network > usb utilities. Tap "connect storage to PC." It'll ask you to connect the cable. Green man pops up and tap "connect usb storage." It's now considered an external drive to your computer.
In regard to when to plug in the cable- that's where it gets picky. If you plug it in and do all this, it spazzes and won't work because the PC is trying to recognize it as an MTP device.
BUT if you have the current drivers, you can just plug the phone in and the computer should just detect it the same way.