Strange download javascript problem

[Guest]

I'm using javascript throughout my siute for basic client validation and a
menu structure.

In a couple of areas I've also code to download to a csv file. As soon as
this code is run anywhere in my site the javascript simply stops working.
Even references to the document object return an "undefined value". Any help
would be greatly appreciated.

Download code as follows:

Response.AppendHeader("content-disposition", "attachment; filename=" +
fileName);
Response.ContentType = "text/csv";
Response.Flush();
Response.Write(fileText);
Response.End();