in your config, you have a maximum width of 400px defined. what happens when this is the case is, the header.tpl file (on the fly) inserts an inline style for .post_inner img that limits ANY image in a POST to 400px..
soooo, when you look at it in a regular post, the photobucket image (which is really 640x400) is resized down to a max-width of 400px..
HOWEVER, the portal page doesn't use the .post_inner img class when it displays a post.. it instead uses alt-1.. totally different..
sooooo, the portal page will display the images with no limitation as they are stored on photobucket...
that's why the diff..
This should be fixed to at least be the same in both places, so you can then decide what your limit will be and have it apply equally
I made the change for you, so it matches now
ps: the simple fix is to open portal.tpl and change line 14 to reference post_inner, instead of alt-1..