closed:CB 1.4 - White Screen if you add a new file

Hi guys,
if i want to add a new field or a new Tab
my screen goes white and thats it, i can't add a new field...
do anybody know this bug?

Jommla 1.6
CB 1.4

Fatal error: Class 'JModel' not found in ....../plugins/editors/jce/jce.php on line 60

THE ANSWER:
www.joomlacontenteditor.net/forum/topic?f=50&p=39266