At the risk of sounding stupid (Im ok with that)

[freygr]

Thanks Terry, but no tap. I'll buy a new memory card and see if they will help.

It's a slide switch, or the contacts on the card or in the camera need cleaning. If you have a card reader you can use it to test the cards read/write function. Memory cards do ware out also but now days it's up to and over 10^6 writes on the newer cards. I remember when they first came out the writes were only 10^3 and 256 bits of memory.