after reinstalling Windows, then i tried internet explorer and chrome; both worked well, showing images and thumbnails.

i then uninstalled completely Opera, reinstalled it and tried the same sites again: it worked too.
the problem seems to have been in config, but i can't see where the setup is wrong.

all's fine now. thanks for the help guys.

(8 hours lost reinstalling Windows and looking for the source of the problem, etc...)

See: http://www.blu-ray.com/community/gallery.php?member=Gelli
or: Axiom Gallery