It appears that January is the only month where the competition is "currently in progress". Images in other months (and there is only one image per month) are quite possibly stock images, not competition entries.
Yep, taking a closer look I think that's it. The slide-overs show up in January gallery.
A happy coincidence is that January's competition is for Guatemala, and I'm going there in November. The Leica is practically mine
edit: Amberley, you might want to clarify your entry rules. Out of the 4 pages of photos in January competition, there is exactly one (1) picture taken in Guatemala. According to your rules
2. The Competition runs each calendar month from 00.01 on 1st January 2011 to 23.59 on 31st December 2011. All times are based on GMT. Entries made before the start date will be entered for January 2011.
which says all entries submitted before January would be entered for the Guatemala (January) competition, thus disqualifying all non-Guatemalan entries. Not sure if that's the intention, and it's clearly confusing to the submitters.