Uploadify和HTTP 401挑战。为什么它不能始终如一地工作?

Using Uploadify plugin which uses jQuery and SWF. Some web servers it works, some it does not. Seems to get a HTTP 401 Not Authorized when attempting to upload. Might be related to SWF. In Fiddler, when it does not work, seem to get this Proxy-Support: Session-Based-Authentication, but when it does work, we don't get the Session Based Authentication. Is this a network routing issue? Proxy Issue? Any suggestions on fixUsing Uploadify plugin which uses jQuery and SW