No clue yet....
Can you post a picture of the bogus chars?
Do you power the Arduino from USB or from a wall wart?
Do you have a voltmeter? if so can you confirm the LCD gets 5.0V
rereading the thread for clues....
Aha, new hypothesis:
On the picture (post 1) you have a 20x4 screen and you initialize it with
lcd.begin(16, 2);
Please try to change that to
lcd.begin(20,4);