I have set up a network at home, connecting an iMac upstairs to another iMac downstairs, which is connected to the internet. I have enable internet sharing between the two, and for a while this worked. However, recently, although the iMac upstairs is connected to the network, with file sharing, printer sharing etc working, it is not able to access the internet at all. The strange thing is is that my Macbook is able to connect to the internet when connected to the network. Does anyone have any idea what has gone wrong?