[kh99]

Well, I don't know then. There's this function (in class_core.php) to determine the path for the <base> tag:

	function fetch_basepath($rel_modifier = false)
	{
		if ($this->registry->basepath != '')
		{
			return $this->registry->basepath;
		}

		if ($this->registry->options['bburl_basepath'])
		{
			$basepath = trim($this->registry->options['bburl'], '/\\') . '/';
		}
		else
		{
			$basepath = VB_URL_BASE_PATH;
		}

		return $basepath = $basepath . ($rel_modifier ? $this->xss_clean($rel_modifier) : '');
	}

so I believe if you have "Always use Forum URL as Base Path" set to Yes then it should use the Forum URL set in the option above that.

Did you change databases when you moved up a level? Do you have any sort of chaching going on?