I'm working with a Windows domain, controlled by a W2003 server. Since installing a number of Windows updates last Thursday (KB948590, KB948881, KB945553, KB941693, KB890830, KB947864) and restarting the machine, some computers on the network have been having difficulty picking up an IP address via DHCP.
This morning I determined that it's only those computers that are not directly connected to the same switch that the domain controller/DHCP server is connected to. The primary switch on the network is a DLink 1248T; there are three other switches linked to the network through this switch, and any computer connected through one of the other switches and whose DHCP lease has expired cannot pick up a new address. If I go to each of the machines and manually assign an IP address, everything works fine.
Nothing else on the network has changed, and this setup has worked flawlessly since it was first set up over a year ago. I have not yet rebooted the primary switch, but will do that at the end of the day when fewer users will be affected by the interruption.