FLASH CS4 - URLRequest or XML?

I have developed a flash site. This site uses URLRequest to execute a CGI program to get data from the backend. The retrieved data is in XML format and therefore, AS3 does XML parsing and processing. The issue that I am having is that some users are able to go to this page and get the data but some users are not able to. With users experiencing issues it does not matter if they use IE, Firefox or Safari. For them, it happens all the time. I am sure it has something to do with browser settings. Could you please help?

Thank you.