I have been connecting to sf.com to read data for more than a year from my app and suddenly tonight it has stopped working.

I have the following exception (I have deliberately removed the username and password, but I have checked that they are correct and refer to the latest security token. 

This was working fine erlier today and I have changed no code...

Method name is: login
'A997F86A-36E9-DDDC-EC6B-BBEE23101466' producer connected.
'A997F86A-36E9-DDDC-EC6B-BBEE23101466' producer sending message 'B89E5879-D7F7-E91E-2082-BBEE231054DD'
'direct_http_channel' channel sending message:
(mx.messaging.messages::HTTPRequestMessage)#0
  body = "<se:Envelope xmlns:se="http://schemas.xmlsoap.org/soap/envelope/"><se:Header xmlns:sfns="urn:partner.soap.sforce.com"/><se:Body><login xmlns="urn:partner.soap.sforce.com" xmlns:ns1="sobject.partner.soap.sforce.com"><username>simon.palmer@*****.com</username><password>*****</password></login></se:Body></se:Envelope>"
  clientId = (null)
  contentType = "text/xml; charset=UTF-8"
  destination = "DefaultHTTPS"
  headers = (Object)#1
  httpHeaders = (Object)#2
    Accept = "text/xml"
    SOAPAction = """"
    X-Salesforce-No-500-SC = "true"
  messageId = "B89E5879-D7F7-E91E-2082-BBEE231054DD"
  method = "POST"
  recordHeaders = false
  timestamp = 0
  timeToLive = 0
  url = "https://www.salesforce.com/services/Soap/u/11.0"
Method name is: login
*** Security Sandbox Violation ***
Connection to https://www.salesforce.com/services/Soap/u/11.0 halted - not permitted from https://localhost/pm_server/pm/pm-debug.swf
'A997F86A-36E9-DDDC-EC6B-BBEE23101466' producer acknowledge of 'B89E5879-D7F7-E91E-2082-BBEE231054DD'.
'A997F86A-36E9-DDDC-EC6B-BBEE23101466' producer fault for 'B89E5879-D7F7-E91E-2082-BBEE231054DD'.
Comunication Error : Channel.Security.Error : Security error accessing url : Destination: DefaultHTTPS
Error: Request for resource at https://www.salesforce.com/services/Soap/u/11.0 by requestor from https://localhost/pm_server/pm/pm-debug.swf is denied due to lack of policy file permissions.

What has changed?