Google changed PR today. I only started on working on those issues two weeks ago. I only got PR3 on some new sites. No impovement on existing sites at all.
Be grateful you're still in the index at all... nice "location"... very classy... are your sites that tasteful and elegant?
For what it's worth. If you read a lot of the different SEO boards, most people went down. So in comparison, staying even isn't all that bad. It's all about rankings anyways, not PR. I have a PR6 site that drives 10% of the traffic that one of my PR3s does.