This patch updates jsMath to properly detect small changes in font size in MSIE. Without this, a font size might not be recognized if the width of a character, in pixels, doesn't change between the two sizes.
To use it, place this patch in the jsMath/extensions directory, and then
include "extensions/patch-2007-12-29.js" in the loadFiles field of jsMath/easy/load.js, or load the extension by hand after jsMath.js is loaded.
Note that this patch is (will be) included as part of jsMath v3.4g, so should not be used once you upgrade to that version.