Button trouble

Hi everyone, I'm new on the forum and I just begin with Arduino.
I have a StarterKit, and I have troubles with the buttons on the 7th lesson on the book, the keyboard. They work once on four. Could you help me please ? What's wrong with them ?
Thank you for your help ^^

Gilles

It is probbly the way you have wired them up.
The resistors go to the arduino inputs and the switch goes to the input and +5V ( assuming they are using pull down resistors )
I always wire across the corners of a switch to make sure I have the right connections.