problem preview with TinyMCE Editor since update!

Hi,
I use the TinyMCE Editor, never had any problems with the preview-button, it always showed me exactly how the new post would look like.
But two days ago I installed the latest version of this template and I noticed quite a big problem when creating a long post with lots of pictures.
When hitting the preview-button, the content of the preview-pane "leaves" its window and continues - literally - over the "Reason for Editing" title, over the attachment-field, over the "submit", "preview" and "cancel" button and then it disappears behind the topic history bar!
Could you check this please ?
For info : I'm using the latest versions of IE and FFx64.