Concrete5 5.8.2.1 - not possible to save text

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Hello everybody,

I have a problem with the new Concrete5 version (5.8.2.1): I can not save text any longer:

I use the "content"-building block (this one with the blue "T") and add some text. If I like to save my work I push the blue "save"-button.
At this moment the little grey processing strip disappears and I can highlight the text now but I am not allowed to save it.
I have no other choice now except to update the page and then the text disappears of course.

Does anyone has a solution for this problem?

Thank you!