validation problems

I entered the following urls into your schema validator:
http://users.rcn.com/rosenshield/courses.xml
http://users.rcn.com/rosenshield/schema.xsd

It gives me this error, which I don't quite understand:

The XML page cannot be displayed 
Cannot view XML input using XSL style sheet. Please correct the error and
then click the Refresh button, or try again later. 


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The download of the specified resource has failed. Error processing resource
'http://www.w3.org/2001/03/style/xsv.xsl'. 


Can you tell me what I am doing wrong? 

Thanks