submenu clicking problem

I got a problem with my wp submenu.
I edited my style.css code to adjust spaces between lines, now it seems like i reduced the clickable area.
‘WORKS’ submenu appears correctly, but as i go to click on a page title, it suddenly disappear.

here’s a link to page: http://www.cristianapalandri.com/site/?page_id=19″

and here’s my style.css code part relative to vertical menu.

/* Vertical Menu */
#vert_m .slidemenu ul{font-size:17px; margin-left:0px; line-height:1; list-style:none;}
#vert_m .slidemenu ul li{position:relative; padding:0 ; }
#vert_m .slidemenu ul li a{padding:3px 15px 5px 5px; display:block; color:#555; text-decoration: none; }
#vert_m .slidemenu ul li a:hover{margin-left:-20px; padding:3px 15px 5px 25px; background:#333; color:#ffae00; text-decoration:none;}
#vert_m .slidemenu ul li ul{font-size:12px; position: absolute; margin:-20px 0 0 70px; left: 0; display: block; visibility: hidden; -webkit-box-shadow: 0px 0px 0px #777; -moz-box-shadow: 0px 0px 0px #777; box-shadow: 0px 0px 0px #777; }
#horiz_m .slidemenu ul li ul li {display: list-item; float: none; margin: 0;}
#vert_m .slidemenu ul li ul li ul{margin-top: 0px; top: 0; }
#vert_m .slidemenu ul li ul li a{width: 200px; background:#333; padding:4px 15px 7px 12px; display:block; margin: 0; border-bottom:0px solid #e9e9e9;}
#vert_m .slidemenu ul li ul li a:hover{width: 200px; padding:4px 15px 7px 12px; display:block; margin: 0;}
#vert_m .slidemenu ul li ul li ul{border-left:0px solid; border-color:transparent; margin-left: 0px; top: 0; }

hope you can help me.