I remember a letter in PCA on this subject. Apparently, when you save files to CD (R or RW) they become read only and you must change the attributes when you copy them back to your hard drive.
I find that if I want to update a file on CD it is easier to copy the new/updated file to the disk (right click and drag the file over to the location on the disk where you want it) then select `Copy Here`. If a copy of the file already exists you will be asked if you want to replace it. Select `Yes` and the file will be updated.