Permalinks, htaccess woocommerce and 404 error

Hi there,
I've tried my best, but my woo commerce permalinks seem broken: http://iie.es/categoria-producto/cursos-generales/cursos-generales-para-adultos/

I followed the threads online to resave etc. my permalinks in wp. But when saving them I've got a blank page.

Something to do with mod_rewrite apparently.

I don't know how to solve this one. I guess it should not be that difficult but not sure my server want to do it...

Please help,
Julien