Steps to reproduce.
1. Multiple file upload with swf file is not working in tomcat cluester environment.
2. Works if we access with tomcat port in all the browsers.
3. If we access with apache port its not working only in fire fox browser.
4. It suppose to make a call to the server to upload file, but without making any call simply says unexpected error occured.
5. Other functinality is working ex. incase of file size is more, may be validated at client side.
Let me know if you need any more information.