Hi steve45321,
Welcome to Microsoft Windows Vista Community site.
This issue is mainly caused by the driver error which is installed for your LAN CARD / NIC (Network card)
The issue can be resolved by downloading and installing the latest drivers for the NIC from the manufacture’s website.
Note: You might need to download the latest drivers in a different computer and install it in the computer where the issue is present, and you must boot to desktop with Safe Mode Option and install the latest drivers for the NIC
Reference Link for how boot to desktop in Safe Mode.
http://windows.microsoft.com/en-us/windows-vista/Start-your-computer-in-safe-mode
Let me know if this worked.
Hope this is helpful.
Regards,
Vijay K - Microsoft Support****Visit ourMicrosoft Answers Feedback Forumand let us know what you think.