Problem in photoslide gk3 with virtuemart

Hi all!

I am trying to configure an eshop using viruemart and k2mart.
I want to use the photoslide gk3 component and module in my frontpage just like the mystore template.
I made the groups and some slides but i take an error message like this :

LOADING
/components/com_gk3_photoslide/thumbs_big/702824daf30d03da42a5291604b3fcca07f0d0_XL.jpg

Fatal error: Class 'ps_product' not found in /public_html/templates/gk_mystore/html/mod_gk_image_show/gk_ps_product.php on line 4505

Could anyone help me?

thnx a lot