pop-up boxes going off screen

Hi folks ..



As you can see from the image that ive uploaded .. my pop-up boxes go to the right of the screen and a portion of the box will disappear. It only does it on 'post reply' - Quick reply seems fine.

I have tried it in numerous browsers IE6, IE7 and the new IE8-RC1, plus Google chrome, and Firefox. I get the same issues in all which leads me to think that it is a Coding issue?
I have also tried different screen resolutions all to no avail!

I have searched the CSS for the template, and as I know very little about CSS, I have been unable to find anything that would make me think that this or that needs changing!

Any help in making these pop up boxes 'sit still' when i use the 'reply post' option would be greatfully received.

Thanks

Id say get rid of the popup boxes OR send me copy off css etc.