iPhone 4 (4.01) won't tether to windows 7

I am using the following: iphone 4 (4.01) jailbroke; windows 7 ultimate laptop; pdanet 4.18 (purchased). I have been trying unsuccessfully to get my iphone to tether to my laptop using pdanet wifi hotspot. I was successful tethering to a friends laptop running windows 7 home premium and he was successful tethering his iphone 3g to my laptop (the same laptop my iphone 4 failed with). I am able to tether using the usb option, but would like to figure out how to get the wifi hotspot to work.

I have posted this problem in numerous forums and also sent to pdanet developer. I have uninstalled/reinstalled pdanet 4.18. I have uninstalled/reinstalled wifi drivers on laptop. I have tried different channels on pdanet. I have reset network settings on iphone. I do not have any other tether apps installed on my iphone.

It is strange that I can tether my iphone to other computers, but not with mine. And other iphones can tether to my computer, but my iphone will not.

Thanks in advance for your help.