Tethering problem iPhone

Hi, I am trying to tether my iphone 4 to my laptop in vista. I did have it working orginally however after an itunes update a couple of months back it now ceases to work.
The phone installs and syncs to itunes with no problems however when I turn on tethering it tries to install the ethernet driver then gives the error -
Apple Mobile device ethernet
insufficient system resources exist etc
I have tried uninstalling itunes as well as removing any registry entries for any apple product on my computer, restarting then re-installing and I still get the same problem.
I have tried updating the drivers in the device manager and get the same result. The driver in the network adapters for iphone has a yellow exclamation mark however no combination of installing, updating, reinstalling the driver solves my problem.
I have tried many solutions found on the net but nothing seems to work.
Any ideas anyon, thanks in advance
Iphone 4 iOS 4 windows vista