This message means that your the drive you are saving to is full or write protected.
If the drive is full:
To check this go to My Computer and click on the relevant drive, you will be able to see on the left hand side how much spare space there is. In most cases anything below 1GB could result in this message. To resolve this you will need to:
Delete files you no longer need.
Backup then delete files from the drive you still need to keep for records.
Move files to another drive
If the drive is write protected:
This will have been enforced by your Network Administrator. If a drive is locked and cannot be saved to you will need to contact them.