The answer is that Storable.pm has a store method and an nstore method. Up to and including 6.2.9, themes are created with the store method, which means they are only valid with the architecture/OS on which they were created. The nstore (network) store method allows cross-platform themes to be created.

These changes need to be made by one who is exporting themes. It has no affect to "fix" broken themes to import properly.

In Attachment.pm:

Change line 28 from:

 use Storable;

 use Storable qw(nstore retrieve);

 store $hashref, $self->getPath;

 bless $hashref;
 nstore $hashref, $self->getPath;