CSS validator parse error using partial attribute selector (~=)

When I run the file at <URL:
http://users.cs.dal.ca/~jamie/course/CS/3172/examples/CSS/tabularDL/ 
tabularDL.html>
through the validator (following the link from the W3C's HTML  
validator) I see the
following two error messages which I haven't seen before:


URI : http://www.cs.dal.ca/~jamie/course/CS/3172/CSS/colours.css
   	68  	html > body > hr#end  	Parse Error title ~=  
"endOfDocumentProper"]
URI : http://users.cs.dal.ca/~jamie/course/CS/3172/CS3172.css
   	237  	html > body > hr#end  	Parse Error title ~= "end of  
document proper"]


The relevant lines from the source files are:

   html > body > hr#end,
   hr[title ~= "endOfDocumentProper"]
     {color:#036; background-color:#036}

and

   html > body > hr#end,
   hr[title ~= "end of document proper"]
     {visibility:visible; display:block; padding:0; clear:both;
      height:0.25ex; min-height:1.5px; width:100%;
      background-image:url(/~jamie/course/CS/3172/Img/jamieDiv.png);
      background-repeat:repeat-x; vertical-align:middle}

I am confident that the first error message (referring to line #68)
is wrong.  I am not so sure about the second message, but I am
surprised not to have seen it before if something really is wrong.

Some more details: the XHTML file is valid, the CSS validator claims  
to be
checking to CSS version 2.1.
--
Jamie Blustein <jamie@cs.dal.ca>