My old, reliable, printer (An HP Deskjet F4280) is suddenly not reliable. It skips all or parts of certain lines in a standard word document. I've cleaned the printer heads and my computer insists "This device is working correctly", but it's not. I have also uninstalled and reinstalled the printer. This seems to be a general problem with any document. Could I have inadvertantly or carelesly messed up the general formatting or something. Oh, I also reset the computer (Windows 7 64-bit)to a point two days ago; no help. Any other suggestions?

This may sound silly,but when was the last time you changed the ink ?
Did you look for a new driver for it ?

If the two devices are talking to each other, the computer will assume it is working correctly. You could definitely have some bad ink. I had a friend who had to take some brand new cartridges back because they were doing exactly what you are describing. Try some new ink and see if it still does the same thing.

Also .... Sometimes using "compatible" ink rather than the genuine brand recommended by the printer manufacturer can cause problems

The new ink fixed the problem. Thanks to all.

Glad it was a simple solution.