Mine's Tahoma as well, and it's not anything that's been recently modified. I found out I can make it stop happening and why it's only been happening for the last week. It only happens when I use the Large or Extra Large font setting in Display properties. Under normal font settings, everything is fine. I've been testing the other font sizes for my WB skin for visionally impaired and had left the larger font size on because I got used to it and forgot about it. So I've narrowed it down that far, but still don't know why it happens.
