Kinda called this one before I had completely read the info. The network driver stacks and protocols are clashing. The ADSL needs one configuration, the wireless LAN another.
With USB doing this hundreds of problems can sneak up, as the stack to make the USB to PCI to south bridge to kernel driver stack to network kernel stack to network protocol to network client to USER to GDI and back again is so complicated I don't want to even contemplate.
It may not be possible to ICS with USB as the USB to network kernel service may be designed only for a single service. You have two going bidirectionally at the same time.
Please try completely removing the entire network and rebuild from scratch. {b}Do not[/b] reboot between settings - if the system, after detecting something or making a settings change, wants you to reboot don't until all settings and component installations are complete.
If need be you may have to go into Safe Mode to remove the network components, don't reboot, go to Control Panel/Add-Remove Programs/Windows Setup/Communications and deselect Dial Up Networking (that is if it was installed), then reboot.
I am not quite sure if this is the solution - but we have to start somewhere. Thanks for trying.
Your mileage may vary...