The system is based on results over the last 4 years. Ghana did well in this World Cup, but don't have consistent results over the last 4 years. You'd expect them to be climbing, though. And they did - up 9 places since the last list. Uruguay and Paraguay were the biggest climbers.
I must admit, I'm surprised England went up. With a win, two draws, and a loss to the team now in 4th place I'd have expected a very slight fall. But remember that their results from Euro 2008 qualifying, where they did poorly, are getting further away so they have less of an effect.
What the rankings don't
do is consider how good a team looked while getting those results.
Edit: the new rankings also include (though with less weight) some recent friendly results:
England 3 - 1 Mexico
England 2 - 1 Japan