What is this called so I can try to find a solution to the problem. This is x.Org, Fedora 19, running XFCE, but I doubt that changes what the problem is called.
When I move my mouse around, there is a bounding box around it which shows through to the xscreensaver screen buffer. By this, I mean that I can see everything on my screen. It is normal. However, there is about a 32x32 pixel square around my cursor which is showing what was on my screensaver when I unlocked my machine. The box moves with the cursor. So, all screen updates work fine outside the box.
From my programming experience, this is what I believe is happening... xscreensaver has a display of its own. When my machine locks, it just switches from the desktop display to the xscreensaver display. When I unlock, it switches back. The mouse is a sprite overlayed on top of the desktop. But, there is a bug. Instead of displaying the desktop display around the sprite, it is displaying the xscreensaver display around the sprite.