Thank you all for your advice - I have decided not to send the camera back but as a computer user, I realise that cameras like computers sometimes get themselves into a freeze state!

Thanks for the quick response. I am just worried that if they cannot replicate the problem then they will simply return the camera or do you think they are obliged to replace it ?

I have a Pentax X5 which occasionally freezes completely and I have to remove the batteries to restart it. Does anyone know if this is to be expected behaviour for this cameras as I have the possibility of returning the camera under warranty but will obviously lose the use of the camera for 4-6 weeks and it may simply be returned as they may not find anything wrong!