Have you recently switched to the new sub-domain? Alternatively, if you haven't, it may have been switched for you -- I seem to recall that everyone would be switched soon. The new sub-domain will make it appear to the search engines that a new site, and all-new content has been submitted. These will have to be re-indexed, and PR re-sets. My own pages re-indexed within a week of the sub-domain switch, but pinging the sub-domain might speed up the process. I think the timeline on that varies depending on how many pages you have, what kind of traffic they're getting, etc.