LCD monitor showing ghosts

Hi All,

my probem is this: the LCD monitor shows ghosts of screen content. If you open any window, folder, etc., a vague stripe appears both to the left and right of the window. It is the same height as the window, and stretches to the edges of screen. It moves together with the window if the latter is moved.
The stripe's brightness (and thus the obtrusiveness) depends on the brightness of the original window.
Similar stripes appear for icons on Desktop, alhough less obtrusively.

What can cause such a thing? Any advice on resolving the matter?

The system is
LG Flatron L1950SQ monitor
Vanta VL2 graphics card
Windows 98
Last week it was working perfectly.

Thanks in advance,

Jimmy