cursed by persistent cursor block

[mike polniak <mikpolniak@adelphia.net>]

This is a weird problem. Usually 2-3 hours after starting my computer,
either in console mode or x-window, a white cursor block (about 10%
larger than actual cursor block size) appears in the center of the 
screen.

This block has a fixed position and cannot be covered up by anything.
I've tried starting and running only the fewest init processes necessary
and a new debian install on another partition.

Sometimes when switching from the console to x-window the block will
disappear for a few mins, but always returns.Any clues where to look?
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