A customer was using MS Proxy 2.0. with NTLM and BASIC authentication
enabled and use JWS 1.0.1 & our jre and everything worked fine but when
they upgraded to MS ISA 2000 with the same authentication enabled, JWS
no longer provides a login popup, and seems to ignore the 407 response
and just fail.

The customer sent in two network traces one with MS Proxy 2.0 where
everything works and the other with ISA 2000 where JWS seems to fail.

WORKS FINE (MS Proxy 2.0):
HTTP: Response to Client; HTTP/1.1; Status Code = 407 - Proxy Authentication
Required
HTTP: Protocol Version = HTTP/1.1
HTTP: Status Code = Proxy Authentication Required
HTTP: Reason = Proxy authentication required
HTTP: Proxy-Authenticate = NTLM
HTTP: Proxy-Authenticate = Basic realm="10.25.231.211"
HTTP: Undocumented Header = Proxy-Connection: close
HTTP: Undocumented Header Fieldname = Proxy-Connection
HTTP: Undocumented Header Value = close
HTTP: Content-Length = 503
HTTP: Content-Type = text/html

FAILS (ISA 2000):
HTTP: Response to Client; HTTP/1.1; Status Code = 407 - Proxy Authentication
Required
HTTP: Protocol Version = HTTP/1.1
HTTP: Status Code = Proxy Authentication Required
HTTP: Reason = Proxy Authentication Required ( The ISA Server requires
authorization
HTTP: Via = .1 SIMISA01
HTTP: Proxy-Authenticate = NTLM
HTTP: Proxy-Authenticate = Basic realm="SIMISA01."
HTTP: Proxy-Authenticate = Kerberos
HTTP: Proxy-Authenticate = Negotiate
HTTP: Pragma = no-cache
HTTP: Cache-Control = no-cache
HTTP: Content-Type = text/html
HTTP: Content-Length = 3761