Occasionally I will open a website and the content will flow below the bottom edge but no scroll bar is available to scroll the content. Page up and down buttons as well as arrow keys will scroll the page. When this happens a page reload will not rectify the issue, nor will opening in a new tab and going to the same URL. However, a close of the browser and then going back to the target URL normally resolves the issue and the scroll bars are visible and functional. FF version 3.6.12 on Windows 7 Ultimate. No specific sites, but experienced this on cnn.com, time.com and morningstar.com over the last couple of days. These are three of my most visited sites and I had not experienced this problem prior to the last update to my current version. I also had a Java update on the same day I did the FF update, so I can not with any certainty pinpoint FF as the culprit.