Try the future pagerank tool at seochat.com. First check to see if your domain has lost its pagerank in all the datacenters. Sometimes when Google are doing a re-shuffle the pagerank vanishes for a day then returns. This has happened to a few of my domains.
Try http://livepr.raketforskning.com/ - it's a bit quicker than seochat dot com, I think. I noticed on one of my sites PR dropped at some DCs, too, although I was expecting it due to having moved this site and therefore updated links in some directories to the new site.