In FF4 Beta 2 - but not Beta 1 - scrolling up can cause a lot of 'smearing' - the same line (and parts of it) appears smeared many times over multiple lines, and there is a lot of jerkiness while scrolling. When scrolling stops the still image is ok. See attached image for an example. The line seen multiple times there appears only once in the actual document. This happens in: 1. Google Docs (shown in screenshot) 2. Zimbra webmail (when scrolling in lower pane) 3. Sometimes in multiline input boxes in HTML Notes: * Scrolling down is ok actually, the problem is just with scrolling up. * I see this on Linux (Ubuntu 10.04 on MacBook Pro), doesn't seem to happen on OS X on same websites. * As mentioned before this was ok in Beta 1 (and before).