What would stretch newreply.php and newthread.php?

[Se?or Ramos]

The "Post New Thread"/"Post New Reply" boxes and the "Additional Options" box on both of these pages are stretched out far further than they need to be. Nothing is there, either. It's just an extra blank space spilling to the right. Where should I begin looking?

Getting a true screenshot of this would've been hell so I made a loose representation on Paint.

[IdanB]

any changes made to template or recent installed plugins ?
guess an un-needed closing table tags like </tr></table> could result with block be "outside" of it's container.

[Se?or Ramos]

Well we've been installing plugins and products left and right. Since there's no easy way of figuring out what caused the problem, I just want to figure out where I would look for this to fix it.

[Lynne]

Try disabling your modifications/plugins and see if you still have this problem.
Note: To temporarily disable the plugin system, edit config.php and add this line right under <?php

define('DISABLE_HOOKS', true);

If you still do, you can run your page through an html validator to figure out the problem. Or, get firebug as a firefox add-on and it will help you. We can't really tell what is wrong just from an image.