LG TinyMCE stripping out CSS classes when entering in HTML mode

I’m trying LG TinyMCE 1.3.3 and have a strange problem with it (or maybe TinyMCE itself, not sure). When I post in HTML code using the HTML button it strips out all my CSS classes. Is there anyway to disable this? I want it to put in exactly what I paste into it.

Any advice/suggestions would be greatly appreciated. Thanks, John