Thought I would start this to put nandroid error codes in one place as well as the fix for them if known. So if u have any and know the fix please post to add to the list.
Nandroid error codes with known issue
14 - Seems to happen when applying a .rom.tgz format. There is too many extensions at the end (I.e. .rom.tgz.tgz, needs to be .rom.tgz) Also could be caused by exracting a .rom.tgz . These files need to be left as a .rom.tgz file.
21 - The file name of the folder has a space in it. ( I.e. nandroid/sample rom, needs to be nandroid/samplerom)
25 - The rom is in too many subfolders. ( I.e. nandroid/samplerom/samplerom, it needs to be nandroid/samplerom
28 - The rom is corrupt somehow, simple redownload or pick another mirror site.
31 - Sdcard has become corrupt. Format through android as your PC may not format it correctly.
34 - This is when doing a backup and there isn't enough space on the sdcard. Delete some files to make room and start again.
35 - The name for the backup is too many characters. Simply rename.