It can be tricky enough to decide which printer will be best suited to your network and then there's the hassle of getting it set up. So it can be even more frustrating when something goes wrong and it suddenly stops working for some reason. If you follow this checklist then you should be able to diagnose the fault reasonably quickly.
You should start by checking out your computer's physical connection to the network (provided it is not a wireless netwrok.). With most PCs there will be a small icon at the bottom of your screen depicting 2 monitors. If you can see a red X between the 2 monitors or if there's an image of a triangle with an exclamation point on it then the chances are that your computer isn't connected (or at least loosely connected) to the local area network (LAN). Check whether the LAN cable is plugged into the network port and that both ends should fit comfortably into their respective connectors. As an additional aid, some PCs have a green light which comes on when a connection is successfully made.
If the issue has still not been resolved after checking the physical connection the next step is to take a look at the internal settings on your computer to see if it is set up for connection correctly. If you are using Windows XP or Vista double click the icon of the two monitors to see how the connection is running. If you see the X between your computer and the server then it would seem that it is your computer that has the issue. In this case you would be best advised to contact your network administrator who will be able to continue the troubleshooting. However, if you yourself have administrator privileges then try clicking the self-diagnosis button to reveal where the problem lies.
If your computer's settings appear to be correct then the next task is to check that the printer itself is connected to the network properly. The best way to do this is to try printing from another computer on the network. If that computer prints find but yours does not then it would indicate that you have not checked your connection or settings thoroughly enough. If you are certain that you have then you may want to try the 'adding a printer option'. Select the printer in your control panel and then choose the "add a printer" option. If you can see that your printer is there but not selected as your default printer then amend this. If you can't see your printer there then choose the option that says "add a network printer". The prompts and instructions should take you through the process.
If you have unsuccessfully tried printing from another computer on the network then check the LAN connection from the printer to make sure that it is properly connected. If the cable is connected properly at both ends then consult the manual that came with the printer to print out the name and IP address from the printer.