Most of you have probably stumbled upon this error when trying to restore a nandroid backup of your rom.
Seen threads at forums with people asking on how to fix this, seeing various tools posted and all that but you don't really need tools for this but a simple text editor. This method has been tested personally by me and it works perfect. Thanks to GalaxyUnlocker for showing me the discovery.
So to begin, you would need Notepad, Notepad++ or any other text editor on your computer.
After you have made your nandroid backup you should know that you have a folder in your SD card named clockworkmod. Inside that folder there should be another folder named backup and after it one with the date you took it.
Inside that folder we've got the nandroid.md5 file in question.
Right-click on it and choose to edit it:
After that you save the file, boot into recovery mode and begin the backup. It should finish succesfully.