Welcome to the Canon Forums and thanks for your post!
To have a better understanding of your issue, please let everyone know what operating system (Windows Vista/7/8 or Mac OS 10.X) you are using.
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To try and resolve this issue, try turning the printer off and back on. Then restart your Windows 7 computer to see if you can print a document once the system loads back up.
If the issue persists, find more help at Contact Us.