XML root not always found

Hi,

We are passing back XML from the database to an ASP page. The XMl is then manipulated using javascript to render the UI in the browser (IE5). The problem I have is that
var root = source.documentElement;
(where source is the id of the XML data island) does not always return the root of the XML even though the XML has been sent back and can be loaded into XML Notepad or IE by itself. Sometimes it obtains the root, sometimes it does not. To complicate matters, a couple of other pagesusing the same method to obtain the root always work without a problem.

Does anyone know why this happens and if so what solutions I can apply? Any help would be appreciated.

Thanks in advance.

Rohit