Virtuemart Checkout problem

hi, i cant get work virtuemart checkout link. when i click on checkout i got an error. as someone wrote in older posts, i disabled Redirect non-SEF URLs and Redirect legacy SEF URLs  in sefadvance configuration.

My site:
www.dero.it
Joomla 1.5.10
virtuemart 1.1.3
sefadvance 2.0.5


SOmeone can help me?

thank you in advance

Did you get this solved?

You have a very good store on your site