Comment 5 for bug 959276

I see this as well and have confirmed it happens in unity 2d as well. The preview pane stops getting updates, so switching selected mail doesn't update the preview pane. For me it happens even without scrolling, but it seems to be most common on very long mails. I can easily reproduce it with launchpad merge proposal emails, so maybe the contents of a diff being rendered triggers something? Maybe a gtkhtml bug?