Is there any chance that a system setting has changed?
Right Click the desktop background > Personalize > Display > Adjust ClearType text > [x] Turn on ClearType
Right Click the My Computer icon or Double Click the System icon in the Control Panel
> System Properties > Advanced > Performance > Settings > [x] Smooth edges of screen fonts
Right Click the desktop background > Properties > Appearance > Effects... > [x] Use ClearType fonts to smooth edges of screen fonts.
Normally, these settng do not change, but I suppose it's possible that a Windows update or maybe a graphics driver update screwed up something.
We would appreciate knowing what your find.