Not knowing what your original problem was or what your trying to do.... its a little ambiguous.
You have a corrupt harddisk of which some photos are salvegable and you want to copy to dvd and are having trouble ?
You have a known good source of photos but when the dvd is near full it fails ?
You keep writing to the dvd over multiple sessions and in the last session it all went tits up ?
If you can be a bit more explicit in what your trying to achieve, why and how its gone wrong it should give us the info to help you more.
As a rule of thumb - dont keep opening sessions on dvd's or cd's, they are not so resillient as HD's and can prove a huge pain. Personally I use even the rw mediums as a once only use - treat it like that and you wont go far wrong.
If you are trying to slavage valuable photos, do it in reasonable sized chunks and move what you have - once checked - file the disk and start on another - the cost of the medium vs value of what your storing dictates how to do this.
It is worth remembering that if a file is corrupt it can give the appearence of a corrupt disk, so if you copy a corrupt file to a disk and it blindly copies it then it can make the destination disk appear corrupt too. If you think your experiencing this narrow it down to file that is the problem if you can.
It may be worthing using something like winzip etc which may ignore/correct these defects and create a zipfile of the whole lot without corruption.
Again, if you can let us know what your trying to do and why - we should be able to advise your further.