Don't know what to say, please go to here http://livepr.ezer.com/ and type www.statcounter.com and you will see their PR is 10 now!! Their history show about 6-8 but now is 10!! What happened??
I guess the big question is ... does it matter? It probably just means that Google changed their algorithm again.
Your right , that is a very strange thing All DC are at 10 => Someone know was append with this site ??? Is that the only site which have a dropping and rising PR ?? (they remove bad link, done a meeting with google . ???)