I have an iMac using ver 10, parallels 9 and Windows Vista. I cannot access the internet from windows. Mac accesses the internet fine. This is a new problem, everything worked fine previously. I have no idea why windows quit accessing the internet.
Open the Vista hardware control panel and check to see if your airport card is working properly and that the drivers are installed. You can also try to run the Windows internet connect wizard to see if that helps.