Canon i470D printing problem

Hello,
I am not totally a computer dummy, I have solved many issues myself over the past years. But I have been stumped with my Canon printer.

The Canon i470D printer has worked fine up until a month ago when the black inked stopped working or printing. After print-head cleanings and a re-boot of the computer, the black ink was working fine for some reason. (!!) I didn't know if it was the print head cleaning or the re-boot that solved the problem? But at the time, I didn't care, because the printer was working!

Then a couple weeks later, same problem. Black ink stopped working. I went online to find another identical printer and bought one off E-Bay. It was a used one and when I connected it, my computer didn't accept it and I didn't know how to make it work, so I put my old one back on.

Note: the only reason I like this one is because of 3 reasons:
1. it fits in my stationary desk (where others don't)
2. ink price is ALOT cheaper
3. it prints close to the edge of the paper where other printers have much larger edge-margins.

After putting my old one back on, I went online looking for advise to clean print heads. Luckily, this Canon print head comes out with ease! and I learned I could soak the head in dish water, clean of course! And I did and when I hooked the clean print head back up, printing went beautifully thru-out the day until the back stopped working AND now the color also!

Why? I have no idea. After the soaking of the print head and getting it good and clean, it worked great as I was able to print several brochures I needed for my home based business. Then both color and black stopped working at the same time.

If you are going to ask if I am out of ink........ the answer is no, I also put in new tanks to be sure.

Any suggestions would be wonderful,
Sandra Thoney
sthoney@att.net