Could you post the code here and it can be checked by others. Also check that your plugin _quicktags.plugin.php is loaded and active. Also the code_highlight_plugin, I'm assuming they are

Hi John,
thank you for reply.
I have installed both plugins.
Some code is not necessary. Even when the Textarea is empty, I get this error and no codeblock is shown.
Perhaps I have to change some group-settings?
But I do not understand all that settings.

I have debugged the script:
I got an unknown exeption at:

window.opener && window.opener.b2evo_Callbacks
&& ( typeof window.opener.b2evo_Callbacks != "undefined" ) )

at line 223 in functions.js ???

Now it is working.
I do not know the reason of the problem.
I assume, the cache should be cleared after installing a plugin.
I didn't clear it.

Good to hear.
Under the Tools tab click on Misc and then the link under "Contents cached in the database "

Usually a good bit of housekeeping :)