Dynamic Menu

I hv created dynamic nested menu where u can show Topics Title or Module Title (have created Module as class for the existing list of menus shown on header menu to make it dynamic) as Menu in the Information control (Left side Menu) or HeaderMenu ascx control.
Problem is, in the vertical menu whn i take mouse over the link it drops the list of child menus, which over laps the existing menus and i am unable to click on the child menus..
But the same works properly whn menu is placed horizontally
This is due to existing css over the Information control..
plz suggest

Classes used are
TOPICS          MODULE           MENU_MANAGEMENT
TopicID          ModuleID          MenuManagementID
Name             Name               MenuID  F.K             for TopicID and MenuID (through code)
ParentID         ParentID          SelInfoMenu             for showing menu list in Information control    
Enabled          Enabled            SelHeaderMenu        for showing menu list in Header menu control
TopicURL         ModuleURL        MenuType               set "M" for Module and "T" for Topic