Sometimes the camera and program are working great, and then all of a sudden, every capture fails.This usually is caused by a disk failure:

• Check if the hard drive is full. You can fill it up quickly shooting RAW files!
• Check if someone moved or renamed the folders out from under you.
• For an external or network drive, check if it was removed or disconnected.
• Check if the permissions for the folder/drive are not allowing you to write to it.