Appearance Different in Some Pages

[gezz]

Hi, I have upgraded to 1.3.9d at my store http://shop.scienceoflife.co.nz and since the last version, I have noticed some of the pages are rendering in strange ways, with enlarged fonts and the sidebars sticking out. This happens in the My Account pages and in some parts of the checkout process.

I only noticed this recently, and have had the site for a couple of years now.

I am using the default template.

What's happening? Thanks!

[gezz]

The funny thing is, when I go to another Firefox tab, and return to the page a few minutes later, it has reverted to normal appearance!