Ok, it sounds like something happened to the printing preferences.  What you can try here is resetting this within QuickBooks.  Try bringing up a Check that you'd like to print, while the check is open on the screen hold down the following keys "Shift+Control+Option', with all 3 held down go to File and choose Print Check.  It should take just a split second but the print dialog window will open.  Then let go of the keys and try printing the check now.  This should reset the printing preferences for you and get QuickBooks back to a default printing state.