Accessing local WebDAV through iframe - problems with authentication

Hi All,
I'm trying to access html pages stored in portal CM subsystem trough
WebDAV from iFrame portlet.
The problem is: when user tries to open the page, webdav subsystem
requests authentication. I tried to set user/password parameter in iFrame
preferences didn't helped, then on this forum found
http://forums.novell.com/group/novel.../@article@1627
but after I turns FormPost to true, iFrame doesn't show the content of my
html files, if FormPost is set to false - iFrame tries to open smth like:
http://username:passwrod@myPortal and surely could't do so.

Tips: exteNd version 5.2.1, portal uses LDAP as directory service, I don't
have iChain or othr auth_proxy, SSO in login portet is turned on