Ok, I'm not sure if any of these will work, but first, try returning true on the onmouseover event. If that still doesn't work, try using onMouseover with the capital M. Those are the only things I can think of.
EDIT: I just checked, and you have to return true. Change your code to this:
$insertpics .= " <td align=\"center\"><a onmouseover=\"window.status='Open Picture'; return true;\" onmousout=\"window.status=''; return true;\" href=\"javascript:opener('$dirName/$jpgFile', $jpgWidth, $jpgHeight)\">\r <img style='border-color:#8888aa; border-width:1px; border-style:solid;' src='$dirName/$gifFile'></a></td>\r";