Flex 4 app behind proxy server w/auth fails to call webservice when launched from IE (firefox ok)

I have Flex 4 app which is deployed in internet.

Just as an intro, when i'm be开发者_如何转开发hind our corporate proxy server, IE and firefox asks for username and password when accessing external websites.

WHEN BEHIND PROXY

In IE (i tested only in 8) Flex app starts fine, but it fails to invoke webservice - CallResponded result or fault event doesn't fire.

In Firefox absolutely the same application works perfectly anywhere.

WHEN NOT BEHIND PROXY

When i'm not behind proxy, everything works ok in both browsers.

BTW

Of course, proxy server address is not known at compile time. Webservice is simple one, no https or credentials needed. Located on the same webserver.

QUESTION IS...

How to modify app or deployment parameters (now they are Flex 4' defaults) so this app can work anywhere, even behind proxy server and opened from IE?

In the top menu try to manage on: Window --> Preferences --> General --> Web Browser

Actual problem was with crossdomain.xml - actually it was absent.

And it turned out that from Firefox i was accessing site with 'www' prefix, so Flash thought it was another domain and refused to load data from it.