[vbat99]

Just tested with your Boston Legal xml as posted above.
Added to Media Companion and then did a right-click, Use Rescraper Wizard on this Show
Selected Series Ratings (TVDb)
and ratings scraped correctly.
Snippit

Code:

<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<tvshow>
    <id>74058</id>
    <state>0</state>
    <title>Boston Legal</title>
    <showtitle>Boston Legal</showtitle>
    <mpaa>TV-14</mpaa>
    <plot>Alan Shore (James Spader) and Denny Crane (William Shatner) lead a phalanx of pricey litigators in a Boston law firm in this series that examines the professional and personal lives of brilliant (and often emotionally stunted) attorneys. For perspective, Brad Chase (Mark Valley) joins the firm to keep an eye on loose-cannon senior partner Crane. Monica Potter, Rhona Mitra and Rene Auberjonois co-star.</plot>
    <imdbid>tt0402711</imdbid>
    <tmdbid>4598</tmdbid>
    <uniqueid type="imdb">tt0402711</uniqueid>
    <uniqueid type="tmdb">4598</uniqueid>
    <uniqueid type="tvdb" default="true">74058</uniqueid>
    <status>Ended</status>
    <runtime>45 min</runtime>
    <ratings>
        <rating name="tvdb" max="10" default="true">
            <value>8.6</value>
            <votes>93</votes>
        </rating>
    </ratings>
    <userrating>0</userrating>
    <year>2004</year>
    <premiered>2004-10-03</premiered>
    <studio>ABC (US)</studio>

Not sure what is happening for you, but I would suggest trying with a clean Media Companion.
eg: rename the Settings folder to Settings.orig
Run MC, and add in the one Series.
Run Batch Rescrape Wizard and selectFor Series to rescrape the TVDB Ratings
FYI for future, wrap the nfo info in the [ code ] bracket for better formatting