In a quick survey I only see that in your first (Newest Photos & Artwork) gallery; I did a view source and it looks as though you used a CSS file that has come through a couple of other people -- any chance the background image you used was in someone else's gallery and they have altered some configuration that shut off direct linking?
The background image specifies:
but at that level I can't tell who it belongs to. My trying to load it directly gets the same "Direct linking denied" error.
If the background is part of your own PBase gallery space, might you have disabled direct linking for the galley it's in? Dunno. I also seem to recall there was some problem with direct linking not too long ago.
Be of good cheer; it's all part of a PBase plan to exercise our brains to prevent Alzheimer's!

DaveT