Issue: IE9 do not animates accordion
My environment: Windows 7 64bit / Internet Explorer 9.0.8112.16421 64-bit edition
Steps to reproduce:
Animation works fine in Google Chrome and Firefox
I think this is a duplicate of the other issue you opened; IMHO, opening one bug for each browser would result in a crapload of issues.
IE9 doesn't support transitions like Chrome and Firefox. Nothing we can do here about this—it's a progressive enhancement.