I had the same problem and Dyson came out. It appears that the older CRo1 memory machines have many bugs that Dyson will upgrade for you free. These being the gear cog that is sticking causing the F15 fault, a new door a new detergent drawer and a new computer. Dyson did all this at no charge as mine was one of the first CR01 ( bought in 2002).
Alas the fault came back after a year, but as they had replaced said gear cog I am back under warranty.
Ring them, engineer will come out after 14 days, I would be surprised if they charge. If they do charge £85, trust me it would be worth every penny to get that lot replaced.
Cheers
Tony
October 2006