All I usually do is connect my device to my PC with the usb cable. Then I click on Internet Sharing on my ppc and then click connect. After a few seconds your PC should show the connection on the taskbar. That's it. I was gonna ask how you do it but I thought I'd explain my way first. I am using vista but I doubt that would make any difference. Some people have had problems flashing roms with 64bit W7 systems but dunno if this is another issue. I'm just thinking that something on your ppc is set so it disconnects automatically after the connection is idle for 5 min or something. It shouldn't just close.
