did u follow the step that are mentioned on the site....I mean the following cases can happen when there is problem is reading the signature ( I think device ID you mean)
1) Baud rate is not properly set i.e. 9600
2) The chip name Like LPC2148 is not set properly
3) Fault in the serial cable
4) May be one need to install proper driver in case use of USBtoSERIAL cable
5) Board itself has faulty chip
you need to check at least first four to conclusion...