Hello.
There is a problem in VirtueMart 2.0.18a - double qoutes in photo description can be saved after product card editing. But when you open this product card again you'll see only that text of saved photo description that was before first double quotes. And if you save product card again full text of saved photo description will be lost.
To fix this you need in \administrator\components\com_virtuemart\helpers\mediahandler.php file in function displayRow change this code:
<input type="text" '.$readonly.'class="inputbox" name="'.$name.'" size="70" value="'.$this->$name.'" />
on this one
<input type="text" '.$readonly.'class="inputbox" name="'.$name.'" size="70" value="'.htmlentities($this->$name, ENT_QUOTES, "UTF-8").'" />