WordPress: I have two search boxes, getting different results from each - Please Fix

Hey guys, We are having problems with the search functionality of a website we are building. Essentially the theme comes with a search icon in the header which brings a full page popup where they can enter a search term. That is not displaying all relevant posts (and in some cases, is finding nothing). So as a test, I added the standard 'WordPress Search Widget' to our sidebar and performed the same search queries, and all relevant posts showed up. WHAT WE NEED: We like the general layout of the search box in the header which only pops up when clicked. Currently it's designed to show a list of all relevant posts in a list inside the popup (but it's not showing relevant posts). What we want is for the design to essentially remain the same, with two key differences. 1. The query, or whatever is making the header search work, we want changed so that it produces the same set of search results that the standard wordpress search widget produces in the sidebar. 2. Rather than displaying a list of posts inside the popup, when someone enters query and clicks enter, we want the popup to disappear and take them to a page full of relevant posts (which is what the sidebar widget search currently does). You can see an example of the two search sections at this link. One search icon in the header (broken/need changed), and the search box in the sidebar. So to confirm, we want the sidebar search functionality, but in the design of the icon/search in the header. [login to view URL] Use both search boxes and search for "Shimano" - the header search gives no results, whereas the sidebar search does. Need work done ASAP.