network users's iPhoto library

Network Users of my OS X Server can login correctly.

As home folder for my network users i set a share from an external firewire 800 hd and i made it available for home directories over SMB (i don't have only Mac in my network).

Now the big problem is that when a user try to open iPhoto he got thie warning: The library could not be opened because the file system of the library's volume is unsupported.

How could be possible? I can read and write inside Images directory.

I read about problems using external hd for home directory. Could someone confirm?

What can I do? When will available an update for OS X Server?

My configuration is Mountain Lion 10.8.2 with OS X Server 2.0 and iPhoto 9.4