1.7 Design => Pages | Saving deletes the page content!

[Lukas Truninger]

I recently updated to 1.7.6.7. Today, I wanted to update some information on a design page. Saving the page did delete the complete page content ( in all languages !!). The other fields (Title, Meta title, ....) seams to be ok.
When I reoppen the page to edit, I get always following text in the page content field: "of 21844 characters allowed". But also this text is not displayed on frontend ....????
I did retest the behavior, writing just "Test" into the page content. Same issue - it is deleted when I save the page. On frontend, the page content is empty (not even "Test"). I did not have this issue with previous 1.7.6.2.