bug? #9 multiplied when switching vom wysiwyg to source view

hello dear fckeditor 2.6.6 users,

I think I found a bug in version 2.6.6 -- or is it a configuartion issue?
The problem affects firefox 3.5 and I could not reproduce it for Internet Explodierer 8.
When you enter a bulleted list into the textarea like this

This is some sample text. You are using FCKeditor.
* 1
* 2
* 3
end

and then switch from wysiwyg to source view several times, the "tab" ( #9 ) is multiplied in
the source code area and so corrupts my text.

I have used the sample code ( sample14.html -- xhtml 1.1 ). The only thing I have changed is
in the config file "sample14.config.js" to be found in the "assets" subdirectory; to be more precise:
<your installation dir of fckeditor 2.6.2>\fckeditor\_samples\html\assets

Here is what I added at the very beginning of the config file:

FCKConfig.ProcessHTMLEntities = false;
FCKConfig.ProcessNumericEntities = true;
FCKConfig.FormatIndentator = '\t';
FCKConfig.TabSpaces = 4;
FCKConfig.ForcePasteAsPlainText = true;
FCKConfig.FillEmptyBlocks = false;
FCKConfig.ToolbarStartExpanded = true;
FCKConfig.FormatSource = true ;
FCKConfig.FormatOutput = false ;

So, please advice.
Is there something I do wrong in my configuration?

best regards
toller43