I don't know if this was your problem (and I know I wasn't here in time to help out), but I'll leave this here for anyone who happens by in the future:
In programming (and therefore in game making) typically coordinates start at 0, not 1. So screen 5 to the right and 4 down would be X 4 (0 ,1 ,2 ,3 ,4), Y 3 (0, 1, 2, 3).
For people not familiar with computer science/programming this is a common trip-up.