E.g. my wife's Mac G5 optical mouse pointer will jump around quite frequently when used on a mouse pad with a print of van Gogh's "Irises", but works perfectly on an old Micron mouse pad with a uniform blue cover. Her optical mouse on her Mac at work would jump around when used on a wood desk without a mouse pad, but works fine with one (also with a uniform cover).
Since it looks at reflected light to figure out how it's being moved, it makes sense to me that if the reflectivity is drastically changing quickly that it might get confused.
Cheers,
Scott.