Display dimming for no reason, and other strange effects

[coadhall]

Hi
I am having a problem with my display. I am using two LCD monitors attached to a Dell Inspiron laptop at work as I work with many documents. Yesterday my main display, a Viewsonic VA2226w started behaving strangely. If I am viewing only the desktop the display goes down to about 30% brightness in about 5 seconds. Moving the mouse pointer up or left/right has no effect. However, if I move the mouse down to half way between mid screen and the bottom, the display brightens to it's normal settings. but only if I leave the mouse there. Returning the pointer to anywhere else and the screen dims again. I have played about with this and found that the sweet spot is a band 1 inch wide equidistant between the centre of the display and the bottom. Moving the mouse all of the way down has no effect. If any dialogue box or normal page is displayed the screen very slowly brightens, but dims if it goes away. The second monitor is not affected, and swapping over the two has no effect, the Viewsonic is still the only one which does this.
It was a bit of a giggle at first but is now getting annoying and making my eyes ache.
Anyone got any bright idea? I called our IT support and they are totally stumped. thanx

 

[Ztruker]

The second monitor is not affected, and swapping over the two has no effect, the Viewsonic is still the only one which does this.

So the problem stays with the Viewsonic. What happens if you connect the Viewsonic to a different computer?
What happens if you replace the Viewsonic?