Unnecessary horiz. scrollbar visible

Hi there,

If the text overflows the iframe, a vertical scrollbar becomes visible. That's ok.
But at the same time a horizontal scrollbar appears. The text on a line is just a tiny bit too long. About the thickness of the vertical scrollbar.

This problem only exists in de the wysiwyg mode. I tried giving the editor a different width, but the problem persisted.

Does anyone know how to get rid of this problem? Im using FCKeditor with PHP and IE6.

All tips or comments are welcome.
Cheers.