There is a problem seen while using navigateToURL in flex. In some cases it causes the user session loss,
To solve this issue, You need to add the session to the URLRequest (in our case we added the jsessionid for TomCat):
var request:URLRequest = new URL Request(“http://www.URL.com” + “;jsessionid=” +sessionId);
And this is also observed that navigaeToURL works fine on some of the browsers like crome,safari etc.
Unfortunately, the information is not covered well by Flex documentation.
Hope this helps people out there facing such sort of issues.