menu items linking to 404

i use the viyo template for a personal website, and when i create a new menu item pointing to K2 categories, it redirects me to 404error page. I thought it is a K2 problem - not working with the Viyo template, so i created everything again in the built in joomla content system. New menu items to the joomla-based articles, but every time i click a menu item, it redirect me to the same 404 error page... I'm desperate, what should i do?

and when it does, it shows me something like the screenshot that follow, where everything is messed up, with no graphics and no style whatsoever! what could be wrong? (the site is in greek)

Hi,
Can you give us url to your site?

after trying everything, i realized that VIYO doesn't support shortened URLs, which caused the problem!