I think you're a lucky person. Sounds very much like a Google bug, but it's a potentially useful look at how the Google back end works right now. In other words, their underwear is showing and you've got a chance for a good look.
When you moved those pages to the new domain, did you put a page-by-page 301 redirect in place? Do the internal URLs also show PageRank right now? And echnoing the question from aakk9999, do you use the canonical link tag? How about base href?
And one final question - do you see evidence in your search traffic that you have "real" PR helping your rankings? ...or does it seem like it's just a toolbar error?