My trackpad does not work properly -- when my fingers are in the middle portion of the trackpad!

I developed the erratic trackpad horror, which seems to be very common, based on the google searches I've done.

I've noticed, however, that the trackpad works normally when my fingers are on the left side or right side of the trackpad.

If I try to drag my cursor across the screen, it gets stuck (or slows way down) in the middle while my fingers move from left to right across the trackpad.

It seems to be approximately the center third of the trackpad where I have the problems. (erratic cursor jumps, not scrolling properly, etc.)

Any ideas?