Greetings. I have a Dell V515w, and my wife's printer is a Dell V313w. (I believe they are made by Lexmark) Both use series 21 cartridges. Both operating systems Windows 7. Both are experiencing the following problem. Sometimes they print with no problem and other times they won't print. When they won't print, the text is held in "Q" and will print after a restart. That is to say upon signing in, the printer will activate. Both have been deleted from their respective units and both have been re-installed.