Membership [renewform] ShortCode Appears to Break the CSS

I'm using Membership 2.1.4 on a WP 3.3 site that has the Twenty Eleven theme (it actually uses a child of that theme, but the following situation arises as well in the 'regular' Twenty Eleven theme with Membership):

Something about the [renewform] shortcode, when logged in, breaks the CSS on the page - in this case my 'Account' page.

This is what my 'Account' page consists of inside Wordpress:

<h3>Click below to access your account information:</h3>
<h3>Click below to access your subscription/renewal information:</h3>

This issue only arises when the user has some kind of subscription running. When they do not, the [renewform] table remains unexpanded, and this doesn't break the CSS. Likewise, when logged out, the CSS of the 'Account' page remains intact.

For some reason I cannot attach a file to this post, so I've uploaded the screenshots here:

Account page when logged out (CSS intact):

Account page when logged in, but without subscription (CSS intact):

Account page when logged in, with subscription (CSS broken):

On the third screenshot you can see how the page background color is missing, and that the footer now extends all the way.

Any help would be appreciated!