Why the heck can't I tether?!

[hpmaxim]

HTC Touch Pro 2 on Sprint, stock ROM. I installed GoodThings2Life's cleanup pack, and the registry fixes, otherwise, its pretty out of the box. I start Internet Sharing it asks me to select between USB or Bluetooth (defaults to USB). I keep it at USB and then click "Connect" on the lower left. The button grays out for a few seconds and then goes back to white. The "Status: Disconnected" remains constant.

I've tried variations on this by plugging and unplugging the USB cable at different times. At one point my Windows Mobile Device Center would ask me what type of connection I was making and I selected "Internet sharing" but it doesn't seem to ask me that any more.

I'm running Windows 7 on the PC.

Can anyone explain whats going on and suggest a fix?