I cleaned up the code and changed the way nested languages works. The IE bug turned out to be an error in IE's handling of innerHTML for <pre> and certain other elements. It was easily worked around by wrapping an extra <pre> around it. I also made the line numbers non-selectable in FF and IE. I haven't shown off line-numbers really, but here's an example:
I generated it at my own computer, obviously using a different style sheet than I use on this blog.
EDIT: Alright, I added those languages. Click here to see the examples.