form submit goes to wrong url

[eluser]SPeed_FANat1c[/eluser]
Hi,

I make a form opening:

Code:

echo form_open ('admin_/naujienos/redaguoti/'.$new_id.'/'.$offset);

And when I press submit button it goes to url http://localhost/darzelis/admin_/naujienos0

I checked the source in browser, I have a good <form> tag

Code:

<form action="http://localhost/darzelis/admin_/naujienos/redaguoti/7/0" method="post">

I have only one form in my page. What is happening there? Maybe there is stupid mistake somewhere, I have no idea