We have some asset share pages that worked on all browsers until about 4 weeks ago. Only with IE11, it is not loading CSS correctly, gives the mis-matched mime type error in browser console (F12), but it's not mime types. On Chrome and Firefox it looks fine, but you should be able to double-click on a thumbnail and it opens up a preview tab with more into on the asset. Going direct to publish works, going through dispatcher it does not. I recall we ran into this when we did the upgrade to 6.3 and it was a caching issue on the dispatcher. If I don't go through dispatcher and go direct to the publish instance at port 4305, it works fine. It's only IE 11 through the dispatcher. Do this ring a bell with anyone?
Thanks for looking!