Hi,
to remove the duplicate widgets in your blog you have to edit blog/code/BlogHolder.php like this:
If you currently have a blog installed, the widget fields are going to double up on those pages (as the blog extends the Page class). One way to fix this is to comment out line 30 in BlogHolder.php and remove the DB entry by running a /db/build.
<?php
class BlogHolder extends Page {
........
static $has_one = array(
// "SideBar" => "WidgetArea", COMMENT OUT
'Newsletter' => 'NewsletterType'
.......
function getCMSFields() {
$fields = parent::getCMSFields();
$fields->removeFieldFromTab("Root.Content.Main","Content");
// $fields->addFieldToTab("Root.Content.Widgets", new WidgetAreaEditor("SideBar")); COMMENT OUT
........
(taken from here: SSWidgetsDoku )
Cheers!