first of all, you don't have a global.ini because this thread was started in 2009 and is related to opsi of at least 3.x, maybe even 2.x, and any information in this thread is pretty much not relevant for the current stable version.
That beeing said, please feel free to open new threads rather than reopen old descussions, it is much easier to understand your problems that way.
Now, from what I understand from your posting, you adjusted the server address correctly, but you did not touch the client.
The client stores the ip of the server it was installed from localy so it can reconnect to it the next time it boots up. If the client cannot find the server, it obviously cannot fetch a new ip address from it

What you need to do is either fix the problem manually by adjusting the clients configuration files, redeploy the client-agent from the new server (manually), or simply reinstall the client with a fresh operating system.
All three ways should be covered by the manual.
Cheers,
Christian Kampka