what does this error means
"java.io.IOException: Server returned HTTP response code: 403 for URL: http://localhost:800/TestDrive/mygabe-debug/gateway.php"
Ok this did not help.
How do I solve this problem
This has nothing to do with Flex. The problem is that your localhost is denying the request. Try getting that url to run in a web browser without returning a 403 error code and you should be good to go.