Limitbox doesn't work properly with SEO links turned off

[sam-m]

I'm using Joomla 2.5.3 and Virtuemart 2.0.6.
On the following page I have placed the LimitBox at the bottom of the template using

Code Select Expand

<?php echo $this->vmPagination->getLimitBox(); ?>
But when I change the selection in this box, in the URL all '&' are replaced with '&' with the consequence that all modules are hidden on that site.
The behavior can be seen on this site:
http://bruderhand.de/index.php?option=com_virtuemart&view=category&virtuemart_category_id=24&Itemid=1130

I have SEO for Joomla and Virtuemart disabled. I'm using a custom template, but the behavior is the same with the original template.

Any ideas how to fix that?