16x2 LCD Mystery [update]

Other Hardware Displays
15

i'd like to inform you that i just bought a 10k potmeter. i tryed but no big results:

this sketch,

// include the library code:
#include <LiquidCrystal.h>

// initialize the library with the numbers of the interface pins
LiquidCrystal lcd(12, 11, 5, 4, 3, 2);

void setup() {
  // set up the LCD's number of columns and rows: 
  lcd.begin(16, 2);
  // Print a message to the LCD.
  lcd.print("hello, world!");
}

void loop() {
  // set the cursor to column 0, line 1
  // (note: line 1 is the second row, since counting begins with 0):
  lcd.setCursor(0, 1);
  // print the number of seconds since reset:
  lcd.print(millis()/1000);
}

witch caused me a full blank screen, is now causing to show about the last 4 or 5 collums black when i turn the potentiometer at a specific moment (i couldn't see them before because i wasn't able to ajust brightness)
i can see them just for a very short time about 50 mil seconds and than they dissapear, wich lets me thinking that the lcd.setCursor(); caused somekind of refresh or reset on the lcd's chip.

questions:

  1. could it be that this lcd is not Hitachi HD44780 Compatible?
  2. how does non-Hitachi HD44780 LCD's react to this libary?
    nick