Thank you very much for your help. I still have two questions.
1) is it the 2.3.5 problem only, or USB tethering is never working with Andriod? I am new to Android, and I didn't get the USB tethering working with 2.3.4 either.
2) I know if I root it, I will get the mobile hot spot working with 3G only. Will the root also give me the USB tethering?
Thanks a lot,