switching from Wysiwyg to Source = nbsp;++

When I Switching from Wysiwyg-View to Source-View and back it produced a lot of &_nbsp;

previous:
<p>bla bla bla</p>
<p>bla bla bla</p>

after 3 x Switch:
<p>bla bla bla</p>
&_nbsp; &_nbsp; &_nbsp;
<p>bla bla bla</p>

Why? My config has the default-settings (lang: de)

Plugins from previous FCKeditor-Versions don't work (ContentLength, nodePath)

I can't say, that the new Version 2.3.1 is stable, but I like one new feature: source-view without popup.