Well, to add the confusion I just tried to reproduce the problem and when I added both a tabbed and accordion from spry it worked fine on IE.
What other updates might have been done? I actually see that your .js files are different than mine. I'm not sure how because the version number is the same, but you seem to have older versions of the .js files. Your .css files worked fine when I replaced them, but as soon as I used your version of the .js files it stopped working on IE for me as well.