Silverlight and cross-domain issues especially with SOAP

I keep having issues with this - mainly due to the examples on the internet and various blogs giving the wrong information. If you want to call a web-service then the root of the website must have a crossdomain.xml that contains:

<!DOCTYPE cross-domain-policy SYSTEM "http://www.macromedia.com/xml/dtds/cross-domain-policy.dtd">
<cross-domain-policy>
<allow-http-request-headers-from domain="*" headers="*"/>
</cross-domain-policy>

Note that lots of the examples have the wrong element name for the "allow..." bit.