I upgraded from Umbraco 4.10 to 4.11 and now when I save a document, all fields are saved except for richtext fields where everything is deleted. Anything I type in richtext editor is lost after saving.
I've had similar problems before with other editors which were caused by html elements and could be solved by uri encoding but I never had this problem with Umbraco and TinyMce.
It was a problem with some customizations that I made in TinyMce that worked well until 4.10 and not working in 4.11 . I don't know why they chose to use TinyMce, CKEditor is way better.