VM+Joomfish Error trying to translate content

[psalamon]

Joomla 1.5.23
VM 1.19
Joomfish 2.17

When  trying to open Joomfish + VirtueMart Products I get the following error:
Fatal error: Class 'mosHTML' not found in /home/miraflor/public_html/administrator/components/com_joomfish/contentelements/translationVm_categoryFilter.php on line 46

line 46 is:
44  if (!$this->filterField) return "";
45      $categoryOptions=array();
46      $categoryOptions[] = mosHTML::makeOption( '-1',_JOOMFISH_ADMIN_CATEGORY_ALL );

can anyone help me with this?
thank you