Our pagerank has dropped?

I find this a bit weird, for a while now we have been sitting pretty on a pagerank of 5 with google but today I notice we have been dropped down to 4.

Obviously google are in the process of updating Pagerank again, but what suprises me is the drop, after so many posts, with so much linkage due to our nomination in the Irish Blog Awards it does not make sense, we have, since our pr5 grown so why put us down?

Any ideas (for it matters anyhow)