Firefox - Displaying Images And Documents Using Across Several Browsers

I have a webpage called DisplayBinaryData.aspx - the purpose of this page being to display/download any word, excel, pdf or images. I call this webpage and pass the id of my BinaryData entity using a querystring. The BinaryData entity contains the file, filename and contenttype uploaded using the asp.net fileUploadControl. The code in the page load is below:

BinaryData obj = GetBinaryObjectById(int.Parse(Request.QueryString["id"]));
Response.Clear();
Response.BufferOutput = true;
Response.AddHeader("Content-Disposition", "attachment; filename=" + obj.FileName);
Response.ContentType = obj.FileContentType;
Response.BinaryWrite(obj.BinaryFile);
Response.Flush();
Response.Close();
Response.End();

This code executes perfect in IE,but fails when executed in FireFox. IE prompts the user, either to save or open the content. FireFox also prompts the user, but the dialog box fails to save or open any content. When executing this in google chrome - there is no dialog box, it starts downloading the content automatically.