WPMU Backend - TinyMCE Editor


We are using WPMU 2.9.1.

We have an issue regarding TinyMCE not wrapping(not sure if this is the correct wording).

Go to any WPMU(maybe WP too) backend >> Post or Page >> Add New -- you see the editor.
Now my screen resolution is 1280 by 800 px, if I change it to 1024 by 768 px, the TinyMCE has a whole goes behind the "Publish" & "Post Tags" box.
The same happens when we press "CTRL & + " on a browser.

How do we get around this issue?

Thanks & Regards