This is not a bug, it's a feature ;-) --- really.
It means, that storeBackup was not able to create a link to a file with the same contents in the backup. Therefore, it had to create a new copy.
The reason for this is normally that the maximum number of hard links is exceeded. This maximum number differs from filesystem to filesystem. It's between some douzens (ram disk) to multiple ten thousands.
If you use a filesystem which does not support hard links (like fat), you will get this message for each repeated version of a file.
Another reason can be wrong permissions (eg. first backup as root, second as user xyz or wrong NFS configuration).
Another reason may be if you have a directory with permissions 0000 and you do not have the permissions to make a hard link to that directory (only a problem if you are not root).
---> Or it's really a bug. Can you try to check the points above? You can eg. try to make a link manually to that file and see what happens.
You can naturally write directly also to me if you want.
Regards, hjclaes