Shared printers

I have a W2K server with W2K Pro and XP Pro clients. I have 3 labs and up to 25 client computers in each lab. One computer in each lab has a printer installed on it and is shared. When I run the Add Printer Wizard on any of the client computers I can make it all the way to where I see the computer that has the shared printer installed. Problem is that when I double click on the computer so that I can select the shared printer nothing happens. I can not finish installing a shared printer on any of the client computers.
I used to be able to do this up until two weeks ago. I don’t know what happened.