access denied to flow service-urgent

iam trying to invoke a flow service from a java client written in WSAD.I set the access permissions of the flow service as anonymous.So i assume that if all access permissions(ACL) are set to anonymous at all levels(package,directory,service),then no authentication is required.webMethods should not prompt for username,password.
BUT this is not happening in my case.I get a access denied exception in WSAD and i tried accessing the same flow service from a browser(IE),and iam prompted for username n password.I dont understand why.
I was able to invoke the same flow service with out any problmes till yesterday.I dont know what happend that today iam just not able to access the flow service.I chekced everything n all seems to be fine.
dont understand.Am i missing something here

please help
any inputs on this will be greatly appreciated

Check port access constraints from webMethods admin->ports.