The server in my office was changed from MS Windows Server 2003 to MS Windows 2008. Since we had the new server put in place, we have to manually authenticate our logins to the servers or shared drives on PCs. This was not happening with the old server before. Can anyone please help?
Do you have a domain based network? If so, it is possible the new server was installed as a non-domain joined workstation which would cause this exact issue. Joining the machine to the domain could be the resolution but I would not do it without speaking to your IT Staff or the consultant that installed the server for you.
If the server in question is the Domain Controller for your network, it may be possible that some or all of the Trust Relationships were broken between the workstations and the domain which would also cause the issue you describe.
You should look at the event logs of the workstations and the servers to see if there are any issues related to the above in the logs.