cannot download zip files in Mozzilla fire fox

I am trying to download a zip file or rar in mozilla but when I save the file it doesn't save properly. It doesn't know the file type. I have include a snippet of code that I am using to downlod the file. If you have any suggestions I would appreciate it. This code works fine in other browser but it doesn't work in fire fox.
 
Dim _EncodedData As String = HttpUtility.UrlEncode(NFNameStr, Encoding.UTF8) '+ lastUpdateTiemStamp 'Set the ContentType 'Context.Response.ContentType = "application/x-zip-compressed" 'Clear the content of the response Context.Response.Clear() Context.Response.Buffer = False 'Set the ContentType Context.Response.ContentType = "application/x-zip-compressed" Context.Response.AddHeader("Accept-Ranges", "bytes") Context.Response.AppendHeader("ETag", """" + _EncodedData + """") ...