Gabriel,
We investigated this a bit, but unfortunately, don't have a solution. Virtuemart is loading child products using an AJAX call which is bypassing parts of Joomla's core functionality, mainly our JFBCSystem plugin. Because of this, our plugin is unable to translate that tag. We're looking into possible workarounds, but don't have anything yet. This is the first time we've heard of this issue, so it may take a little bit of time. It's also something that may need to be brought up with the Virtuemart developers.. specifically, how to enable the system plugins on a child product page.
We'll let you know what we find, but until then, we agree that removing the tag is the best option.
Alex