1.Close all notebooks (will delete the corrupted cache)
2.Open them with the Office Web App using your browser
3.Open them from within the browser using “Open in OneNote” (the cache is rebuild)
Maybe not such a big thing for thoose who have been evaluating and providing feedback on the Microsoft Office 2010 Technical Preview, but the Office 2010 beta is a big step forward even for us. My personal favourite is ofc OneNote 2010 as a tablet PC user.
Be sure to try it out!