Sfly,
Just out of curiosity, did you mean to say that one of the FMCs refused the input? If so, certainly you had the other available. You could play with the stubborn one while the good one did the flying.
I have had an FMC totally dump just after coast-out...just go blank....with the associated FMC failure messages. The other FMC worked perfectly, as I assume was the case for you. However, I am not familiar with the A330.