> I have a Logitech optical wheel mouse here (the kinda with the little ir light
> to detect movement.)
Are you sure it's IR light? Not just red? A friend of mine changed the standard red led with a high-intensity blue one, and the mouse still works. I can guess that the red led can shoot in the IR band too, but the blue one surely doesn't, so the sensor must be a wide-spectrum photodiode.
> Anway, it keeps going crazy and moving the cursor to the
> bottom left and some times top right of my screen. It seems to be random and
> i'm not sure when it started, but i haven't been using a mouse pad recently
> (mine got trashed) so i' sliding it along my flat desk surface. I'm wondering
> if maybe particles on the desk are shooting it in odd directions?
Very likely. Particles, and odd reflections given by an irregular surface, for example. It happened very often with mine as well, I thought it was malfunctioning 'cause I bought it at a flea market in the original "to be sold together with a computer" package :) but changing the rough, coloured mousepad with a smooth and monochromatic one (from the 486 days when mice were rarely used and mousepads were a luxury) was enough to end all my problems. Can't run it on my desk 'cause there's glass on it :P