if the LCD is showing results without pressing any key on key board???
hummm….
1) what exactly the key interfacing type you using… R u sing the same key pad which is shown in the ckt…. or providing an extra ground or Vcc in the keypad ckt….
2) check out if there is any short connection that might causing you that problem..
3) random key means? does the LCD shows one or more key with a continuous sequence or there is no sequence…
4) have you pressed any key and check weather it is showing that key on LCD or not????
check those things and let me know…