It’s a basis design part of the jqGrid implementation. Do you tried to set fixed height (some integer value) of jqGrid, so that vertical scroll bar appears? In the case the vertical scroll bar exist only in the body of the grid. During vertical scrolling the column header (which can contains searching toolbar or other elements) will stay on it’s place and only the grid data will be scrolled. There are some implementation alternatives which have always some disadvantages and restrictions in different version of web browser. So one have to make a choice and to follow it.

Best regards
Oleg