To me, it sounds like your Black Cartridge is not working. It can print the color squares (Probably Yellow, Magenta, and Cyan) and one black square (which was probably printed using the three color cartridges). The areas printed using only the Black cartridge were missing.
To test this, open one of your Notepad files using WordPad instead of Notepad. (Start -> All Programs -> Accessories -> Wordpad). Once in Wordpad, select all of the text and change the color of the text from Black to Blue using the small arrow beside box at the top with the "A" with a thick [black] line under it. Then try printing it again. It should print in Blue. If you change it back to Black and it won't print, then almost for sure you have a problem with the Black cartridge. Unless your old black cartridge was totally empty, try putting it back and see if it works again. You may have gotten a bad black cartridge.
HTH,
JW
Thank you for addressing my problem, but when I tried your suggestions, I still can not print black text. I've even replaced the new black cartridge with another new black cartridge and the problem still exists. When I printed from Wordpad using the blue...it printed ok. I've tried using the old original black cartridge, too, and it didn't print either. I've cleaned the print heads, removed and reinserted the cartridges, made sure the "vent" was clear, and even removed and reinstalled my printer. I've gone through all the solutions of the hp help menu and still have not been able to figure out what happened. I cannot believe that changing the ink cartridges would cause something like this, but evidently it has! Thanks again for trying to help......I truly appreciate it.
Bob