Drop down menu

i am using the wptouch for the mobile version of my website http://www.wikipharmapedia.it . i have a problem, the drop down menu disappear when i click on the end tab on the iphone, to be able to see all the dro down menu. all the drop down menu disappear when i click on END. Any idea for a possible solution ?

http://ww.wp.xz.cn/extend/plugins/wptouch/