Actually I am developing one plug for windows live writer. for that I made this class
using System;
using System.Windows.Forms;
using WindowsLive.Writer.Api;
using System.Net;
using System.Reflection;
using System.IO;
using System.Collections.Generic;
using System.Text;
using System.Collections;
using WindowsLive.Writer.BlogClient;
using WindowsLive.Writer.CoreServices.Settings;
using Microsoft.Win32;
using WindowsLive.Writer.BlogClient.Clients;
using WindowsLive.Writer.CoreServices;
using WindowsLive.Writer.Mshtml;
using System.Configuration;
using System.Text.RegularExpressions;
using System.Drawing;
using System.Drawing.Imaging;
namespace SamplePlugIn
{
[WriterPlugin("a285f0bc-81ba-44ef-b1e0-70700cf62ef0", "Gallery Plugin",
Description = "Server Gallery pictures.",
- Show quoted text -

HasEditableOptions = false)]
//ImagePath = “Images.writer_thumb.png”,

[InsertableContentSource("Picture Gallery", SidebarText = "Picture Gallery")]

public class Plugin : SmartContentSource
{
public override DialogResult CreateContent(IWin32Window dialogOwner, ISmartContent content)
{
DialogResult result = DialogResult.Cancel;
try
{
RegistrySettingsPersister persister = new RegistrySettingsPersister(Registry.CurrentUser, “Software\\Microsoft\\Windows Live\\Writer\\Weblogs”);

string[] names = persister.GetSubSettings();
for (int i = 0; i < names.Length; i++)
{
ISettingsPersister blogPersister = persister.GetSubSettings(names[i]);

SettingsPersisterHelper settings = new SettingsPersisterHelper(blogPersister);

CredentialsDomain domain = new CredentialsDomain("name", "description", null, null);

BlogCredentials creds = new BlogCredentials(settings, domain);

string blogName = blogPersister.Get(" BlogName ") as string;
string apiurl = blogPersister.Get("PostApiUrl").ToString();
if (apiurl == Global.MetaUrl)
{
Global.userid = creds.Username;
break;
}

}

if (Global.userid != "")
{
PluginSettings settings = new PluginSettings(content.Properties);
using (frmMain form = new frmMain(content))
{
result = form.ShowDialog();
}
}
else
{
result = DialogResult.Cancel;
}
}

catch (Exception ex)
{
PluginDiagnostics.DisplayError("CreateContent", ex.Message);
}
return result;
}

public override string GeneratePublishHtml(ISmartContent content, IPublishingContext publishingContext)
{
string str = "”;
try
{
str += “”;
}
catch (Exception ex)
{
PluginDiagnostics.DisplayError(“Generate Html”, ex.Message);
}
return str;

}

public override SmartContentEditor CreateEditor(ISmartContentEditorSite editorSite)
{
return new ContextEditor();
}
}
}

Its actually one picture upload plugin but when GeneratePublishHtml method return, it add default tag in between my generated html tag which i dont want and due to that it is not going to call MediaObjectInfo IMetaWeblog.NewMediaObject(…) from metaweblog api so that picture is not going to be save on my server….

I have the same problem as described in this link which i got yesterday when i was finding a solution for above problem..
http://social.msdn.microsoft.com/Forums/en/wlwdev/thread/f555955a-b96d-4e13-a078-f12df240393d

Thanks for help….