Download file as attachment problem

hi all:

I have a very strange problem here. I have a webform with a gridview. inside this gridview i have a linkbutton. in my rowcommand event for girdview. I have some code like

int index = Convert.ToInt32(e.CommandArgument);
Attachment attachment = Attachments[index];
Response.ClearHeaders();
Response.ContentType = attachment.MimeType;
Response.AppendHeader("Content-Disposition", "attachment; filename=\"" + attachment.Title + "\"");
byte[] data = attachment.GetContent();// t ...