In this case, I don't think it is cookies. Both paths are set to / and the domain on both are set to .aawforum.org.
In this case it would be someone who has cleared cookies or has never logged in.
If you have never logged in or are logged out and we direct you to a photo upload page
Login - AAW Photo Gallery
I get the photopost login. If I login there, it still show the vBulletin info in the top right as (username instead of Welcome ...) not logged in.