Hi Bill,
Thank you very much for your help. It seems to have resolved the problem. I was infact using 8Mhz rather than 16Mhz.
My AVR is Atmel Mega 328P-AU.
This AVR is 20Mhz on the datasheets. Do you suggest I do anything custom about it or just continue using the standard 16Mhz option in my IDE?
Thanks Again !
Simon