tib-file empty?

Hi!
On a Linux System (Ubuntu) I make backups of two partitons (ext3) for a year and longer with ATI 11 booting from a CD. After backup I attach the ext. harddisk to my Windows-System (XP) with an installed ATI and I can see with the explorer the files in both partitions.
That's what was. Sindce the last 4 backups I can see with the explorer only the files of on partition. The other driveletter shows no files.
Today I took an empty harddisk and first I restored an older backup of the two partitions. On the Ubuntu-system I saw both partitions. After that I restored the last image that shows no files on the corresponding partition. The time of the restore-process was normally long, but afterwards the Ubuntu-system only showed one partition. The other, recently restored partition was not there.

What happened to my system that it seems the backup is made, but afterwards only one partition is able to be restored. A validation af this dubious ended with everything ok.

Thanks for your helpful comments!