You need to find the policy that did the dirty work and disable it. Use gpresult to find the policy.
Run gpresult /v > gpresult.txt at a computer with no access to Network and Dialup Connections. Use Notepad to read the text file. Look through each policy until you find the one that did the damage. Use the Group Policy Editor to disable the policy (or set it to "Not Configured."
This was first published in May 2001