I think the cause may have come to light in the because I used my 4 serial number to upgrade to 5 it has blocked out my 4 serial number. I did explain to Curious Labs that I lost my 5 discs and documentation in a fire at my home so reverted back to using 4. I have requested them to re load my 4 serial number in to their system so that I can then upgrade. No doubt they will say 'No' and tell me to purchase a relacement version of 5 :-) L13RAF