Strange lower third "mask" on desktop

Today I noticed that icons on the lower third of the desktop were only showing the top half, as if some video editor had used a "mask wipe" effect to hide the lower third of the screen using the background as the mask.

That TV term is the best way I can describe what is happening. If I drag an icon past that invisible lower third border, it disappears, never to be seen again!

This is very strange.

Welcome to Windows Seven Forums.

Go to Control Panel>Appearance & Resolution>Display>Screen Resolution and check what it's set at.

Excellent...it was set to 75Hz which was making everything screwy. Thanks.

You're very welcome. Thanks for the feedback.