Listview - Reverting Response Header?

've programmatically created a listview, for displaying images. When you click on the download the ItemCommand is fired, and the browser sends the user the image as a binary response, using the following:

SPFile ImageIfile = spfolder.Files[ServerName];
byte[] bs = ImageIfile.OpenBinary();
string res = Page.Response.ContentType;
Page.Response.ContentType = "image/jpeg";
Page.Response.AppendHeader("Content-Disposition", "attachment; filename=" + Path.GetFileName(fileName))
Page.Response.BinaryWrite(bs);
Page.Response.End();

This works, exactly once. Then neither the download link, nor the DataPage paging controls
work until you refresh (Indeed any postbacks).

EDIT: It's a SharePoint 2007 WebPart, this is the declaration of the ListView in the CreateChildControls method:

lv.ItemPlaceholderID = "itemPlaceholder";
lv.GroupPlaceholderID = "groupPlaceholder";
lv.ID = "MediaSearch";
lv.LayoutTemplate = new LayoutTemplate();
lv.GroupTemplate = new GroupTemplate();
lv.GroupItemCount = 4;
lv.ItemTemplate = new ItemTemplate();
lv.EmptyDataTemplate = this.Page.LoadTemplate("/usercontrols/MediaResults_Empty.ascx");

And this is the ItemTemplate and DataBinding

public class ItemTemplate : ITemplate
{
public void InstantiateIn(Control container)
{.....