I have a new wp3.5.1 installation using the Marketpress plugin along with the default Simplepress theme.
I found an error the Marketpress plugin that is shifting the price.
Take a look at the attached screen shot showing the product listing in Chrome.
Similar shifting occurs in IE 9, Opera and Firefox.
The error is happening from an inline style declared in template-fuctions.php, line 1494
<div class="mp_price_buy" style="width: '.$width.'px; margin-left:-'.$width.'px;">
On my code it's showing as margin-left: -150px. When this is disabled, the categories are displayed correctly.