All the things mentioned can cause the cr error, there is one other thing that causes it on our machine the small tab on the left hand lower edge of the carriage that holds the head back and is operated by a soleniod I think, its the little slide you lift to free the head carriage, well every morning if we don't operate that by hand as it is a bit sticky then when the machine initiates it gives the cr error, my morning routine is to operate it by hand slide the crariage in and out then switch on we never have any bother again after that and it prints all day.
Now I know somebody will say clean it but believe me we have but every morning it is stiff but once operated is fine.
regards
Tel