Vista - Odd permission problem

Just two days ago I bought a brand new Core Duo 2 PC with an OEM Vista Home
Premium.
Most of the issues are to be expected and I can always find a workaround,
except this one:

I'm using Good Sync (freeware) to copy stuff from my old (not yet?) XP to
the new Vista over a private network. It all worked normally until I
started getting "access permision" errors when copying *some* files (regular
camera pictures). At
first I though it was some subtle bug in Good Sync, or a network issue, but
no, there is a genuine, persistent, access problem.

And quite odd btw:

From the Vista machine, using windows explorer, I can see the
folder on the XP machine. If I click on, say, Picture1.jpg, I can see it in
the preview, see its metadata, copy it to a Vista Folder, etc, etc.. no
problems.
Now if I click on Picture2.jpg, I can not see it (the preview), copy it,
etc... somehow I
don't have permisions for **that** picture (as the Security tab reveals).
The same happens with a bunch
of 50 or so pictures in that folder.

Now, from the XP machine, using again windows explorer, I can't see any
difference whatsoever between Picture1 and 2, they both have the Archive
Attribute set and nothing else.

And the problem is persistent. Rebooting both PCs doesn't change
anything.The exact same files are unaccessible from Vista.

Any clues?

TIA

Fernando Cacciola