To get fresh version of toolbar & PR rather than cached & then check for Greyed out PageRank pages: delete search history from the Google Toolbar, from the Google search box, and from your browser

Google Toolbar FAQ: "Why doesn't the PageRank button display anything?
If you are behind a proxy web server or a firewall, it may be interfering with the Toolbar's requests to extract PageRank information from Google. Try out one of our experimental features, designed to fix this problem. Click on the Google logo, and from the drop-down menu select (or press the Options button) to access Options. Select the More tab in the Options window then check the box next to the option Fix PageRank through proxies (experimental). Alternatively, you can disable the Advanced Features entirely on the Google Toolbar. To do so, click on the Google logo, and from the drop-down menu select Help > Privacy Information. Uncheck the boxes listed under Advanced Features.
Note that the PageRank display will not automatically fetch information from pages with CGI arguments (that is, pages with a '?' present in the URL)."