Osx Error Connecting to Windows Network


I am trying to connect a G5 with OsX to a Windows 2000 network and am able to browse the internet but cant print or login to a network machine. Actually I used to be able to print and to login to machines but now when I browse the network and click on a machine I get the login prompt and I get a message such as "the original item could not be found" the the login prompt comes back.