Nero, Data Verification Failed. Multisession. Can't Open Old Files

Hi, can anyone help. Just added some new files to a multisession disc. Have done this many times before with no problems. This time the data verification failed. Result, can't open the disc. Problem, most of the old files on the disc are no longer available to me and it's begining to look like I've destroyed my only back up. I know if I can get the old files off the disc I can start again on a fresh disc, but with the disc not opening... Well, you get the picture. Ideas anyone?

 

It's alright, I've got the disc to open and the old files are off and backed up elsewhwere.

 

sometimes when nero burns multisess it does this weird thing where it creates a totally new burn & your previous burn is no longer recognised so to speak,you should be able to use explorer & open the disc that way & the folders will appear fingers crossed,apart from that i can't help