Hey Abs,
Not sure if this is going to help...however, what you might
want to try to do is convert that PPTX to a standard PPT 2003
presentation and then republish the deck. I seem to remember that
this issue was reported awhile back by other users, but I can't
find the post in the forum. Again, not sure if that will do the
trick, but might be worth a shot nonetheless.
Rob