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60 Chapter 4 Troubleshooting
The screen freezes.
 Force the frozen application to quit. Choose Apple () > Force Quit and select the
application.
 If that doesn’t work, force the computer to restart by pressing the power button (®)
for 5 or 6 seconds until your Mac Pro shuts down. Press the power button (®) again
to start up your Mac Pro.
The light on the front of the display is flashing.
On some Apple flat panel displays, the power light displays a series of short flashes
when an error is detected.
 If you see a repeating sequence of three short flashes, the display is detecting input in
the wrong video format. Make sure your display is compatible with your graphics
card and that you’ve installed the correct display software, if your display came with
installation software.
 If you see a sequence of two short flashes and a long flash, the display is detecting a
problem with a backlighting lamp. Contact an Apple Authorized Reseller or Apple
Authorized Service Provider.
Problems with Your Internet Connection
If you have trouble with your Internet connection, you can try the steps in this section
starting with Network Diagnostics.
To use Network Diagnostics:
1 Choose Apple () > System Preferences.
2 Click Network and then click “Assist me.”