Where did my homepage PR go?

My Google Toolbar got corrupted about two weeks ago and I didn’t pay much attention to it, all sites I visited Pagerank were showing “No PageRank Information Available”. On this blog my PR was 3/10 for almost several months now. I reinstalled the Google Toolbar last night and saw that my PR has vanished. From what I know this happens only when you get banned from Google from doing some Black Hat SEO tricks. Well I wasn’t doing any, plus some of my post still has Pageranks but not the homepage. Researching it further I found this is happening to some sites owners as well. No one has a clue. I checked Google Webmaster Tools and my site is being crawled periodically, I checked my log files and .htaccess file.. all is well.

So far the only thing not right is the robots.txt file which I rarely modify has no data in it. It’s missing

User-agent: *
Allow: /

So I added it back and I’ll check in the next few days if my PR returns to normal.