Without the image, it pauses just fine in both IE and FF. This leads me to believe that the onmouseover/out pause event should be assigned to the area tag and that a default area tag should also be used with this onmouseover/out event attached:
HTML Code:
<map name="m_map">
<area shape="rect" coords="374,298,412,337" href="http://www.google.com" target="_blank" alt="" onMouseover="copyspeed=0" onMouseout="copyspeed=slidespeed">
<area shape="default" title="" nohref onMouseover="copyspeed=0" onMouseout="copyspeed=slidespeed">
</map>
Worth a shot. Also, giving the images dimensions might help.
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