HTML and Umlauts not getting displayed properly all of a sudden

Did you do any upgrades, change any plugins, or paste anything into your draft which had come from another location which might have had previous code associated with it? What is your database and tables charset? Have you tried deactivating plugins? If you provide a link to your site someone might be able to better see what is going on.

I know what happened. I have a plugin installed: page autolinks. It creates an autolink to a page whenever it finds the page name in the text somewhere.

I was creating a new page that had no title and saved it as a draft. Now the autopagelinkplugin does not differentiate between published pages and drafted pages so it tried to link every effing nothing to the draft page which cause wp to have hick-ups and forget to parse.

You should have seen all the hrefs in the source code ??