Media upload screen format problem

Hello
I am having a problem with the Media upload form.
When it is called from the post-new.php it appears in the lower middle of the screen and only shows 50% of the form.

If I insert the full url of media-upload.php in the browser bar the full media upload screen appears.
Not being an expert at php I can only guess its a CSS problem in positioning the Media-upload.php in the iframe..
Can anybody shed some light on this..

I have uploaded the latest version of wordpress and done the usual delete and uploaded

Thanks