Today I tried to access a SharePoint REST API from my Silverlight Web Part and I got a Security Error. I quite quickly got a great article describing all about the clientaccesspolicy.xml, but it was still not working.
Then I tried in my browser to go to http://myurl.mydomain.local/clientaccesspolicy.xml and I found that a previous version was being displayed in my browser. I did an IISReset, but this file didn’t want to be updated. I cleared the browser cache and my file got updated. Quite annoying … browser caching.