I solved this on mine by removing and reinstalling the print head.
1. Remove and set aside the ink cartidges (don't make a mess)
2. lift the gray print head lock lever that is to the left of where the ink cartridges go.
3. Lift out the print head out without touching the ink ports inside, the contacts on the back, or the print nozzles on the bottom. The print head is the grey thing with circular ink ports that seat the ink cartridges. there are good pictures in the PDF of the Easy Setup Instructions available on the Canon Printer website. Look under the printer, then support, then downloads: http://gdlp01.c-wss.com/gds/0900002776/mp510_esi_us_v2.pdf
4. Put the print head back in, lock the lever, reinstall the cartridges in the roper positions. And voila!
If this doesn't work you may actually need a new print head.