This is still a problem and is super strange.
Is this exposing an underlying SilverStripe problem? Only SilverStripe sites listed on poweredsites.org exhibit this behaviour - except for Vitesse's own SS site.
I thought I'd provide a shortened URL via TinyUrl and goo.gl as a workaround but still the same.
Below is the GET header summary:
Request URL:http://www.markwaltersmediation.com.au/
Request Method:GET
Status Code:404 Not Found
Request Headers
Accept:text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8
Accept-Encoding:gzip, deflate
Accept-Language:en-us
Cache-Control:max-age=0
Referer:http://sites.poweredsites.org/markwaltersmediation-com-au
User-Agent:Mozilla/5.0 (Macintosh; Intel Mac OS X 10_7_4) AppleWebKit/534.57.2 (KHTML, like Gecko) Version/5.1.7 Safari/534.57.2
Response Headers
Accept-Ranges:bytes
Cache-Control:public
Connection:close
Content-Encoding:gzip
Content-Length:4334
Content-Type:text/html; charset=utf-8
Date:Wed, 25 Jul 2012 01:56:26 GMT
Etag:"35ef-4fb1f559-0"
Last-Modified:Tue, 15 May 2012 06:19:05 GMT
Server:LiteSpeed
Vary:Accept-Encoding, User-Agent, User-Agent
X-UA-Compatible:IE=Edge,chrome=1
And below is the normal GET header summary:
Request URL:http://www.markwaltersmediation.com.au/
Request Method:GET
Status Code:200 OK
Request Headers
Accept:text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8
User-Agent:Mozilla/5.0 (Macintosh; Intel Mac OS X 10_7_4) AppleWebKit/534.57.2 (KHTML, like Gecko) Version/5.1.7 Safari/534.57.2
Response Headers
Cache-Control:no-cache, max-age=0, must-revalidate, public
Connection:close
Content-Encoding:gzip
Content-Type:text/html; charset="utf-8"
Date:Wed, 25 Jul 2012 01:59:50 GMT
Expires:Thu, 19 Nov 1981 08:52:00 GMT
Pragma:no-cache
Server:LiteSpeed
Set-Cookie:bypassStaticCache=deleted; expires=Thu, 01-Jan-1970 00:00:01 GMT; path=/; httponly, bypassStaticCache=deleted; expires=Thu, 01-Jan-1970 00:00:01 GMT; path=/; httponly
Transfer-Encoding:Identity
Vary:Accept-Encoding, User-Agent, User-Agent
X-Powered-By:PHP/5.3.10
X-UA-Compatible:IE=Edge,chrome=1