No matter what type of printer you use, it is important to have some basic troubleshooting skills under your belt. There are a number of issues that can cause a printer to stop working and lose communication, and working through those problems one by one is the best way to get your printer back up and running.
Walk over to the printer and print a test page directly. The procedure for printing a test page will vary from model to model, so you may need to consult the user guide that came with your printer. For most network printers, you can print a test page by navigating the "Information" menu on the control panel and choosing "Print Configuration" from the menu. For many desktop printers, you can print a test page by holding the power button until the page begins to print. If you can print a test page from the printer, but not from the computer, you know there is a communication problem between the printer and the PC.
Remove the printer cable from the back of your printer and the back of your computer. After the cable has been removed, carefully put the cable back into place, making sure that the printer cable is tight. If your printer uses a parallel cable, be sure that it is fully seated on the back of the printer and on the computer. If you are using a USB cable for your printer, be sure that the tab is fully seated in the computer, and that the square end of the cable is firmly connected to the printer.
Power down the printer, the restart your computer. Click on the "Start" button and choose "Control Panel" from the menu. Double-click the "Printers and Faxes" icon, locate your printer, right-click on it and choose "Properties" from the menu. Click on the "Print Test Page" button to send a test page to your printer.
Look at the network card on your network printer to see if there is good communication between the printer and the network. You should see a flashing green light on the network card. If there is no light--or if the light is amber or red--the communication is not happening. To test the network communication, remove the network cable from both the network cable and the network port on the wall, then reseat the cable and check the communication again. If the problem remains, you will need to remove and replace the printer's network card.