For security reasons, a Macromedia Flash movie playing in a web browser is not allowed to access data that resides outside the exact web domain from which the SWF originated.But there are workarounds:
1) use a crossdomain xml file that sits on the server and tells flash which domain it can access. http://www.adobe.com/cfusion/knowledgebase/index.cfm?id=tn_14213
2) use a php proxy script – like discribed here http://www.thegoldenmean.com/technique/rssReader03.html
with this option though you need to implement a kind of security because any hacker could potentially use the proxy and make calls with to the db or to other files like .haccess and find out passwords. Maybe send a string as code. Flash could send astring every time it makes a request that the php can use so it knows that it comes from flash and therefore is legitimate.