I assume you are using the Arduino LiquidCrystal library which is written for an HD44780 (or compatible) controller which can deal with displays having up to 80 characters.
Your display obviously uses a different controller since your display has more characters. On the other hand its controller probably has a somewhat similar instruction set since your display is legible.
That's about all I can come up with given the minimal information you have provided.
I did enjoy reading the early responses.
Don