I'm running WLM 2011, Build 15.4.3555.0308 on Windows Vista.  I'm not sure when this situation started, perhaps with a recent update.  When I'm in the body of a message, sent or received, text or HTML, and use the scroll wheel to scroll up and down, the action is hesitant and jerky.  Using the scrollbar beside the pane works fine, and using the scroll wheel in any other program, Microsoft or not, is smooth as silk.  Am I alone, or has anyone else experienced this?  I know that the scroll wheel used to move the text up and down nicely.