WordPress MU

I have a internal bloging system for a company build on wordpressmu2.7 installed on windows server 2008 and IIS7 and I use LDAP for users creation, the problem is that I want to enable IIS basic authentication and windows authentication in the same time, but when I do that, the basic authentication do not work and give me error message
"password field is empty"
the resone that i use both is that in this company the authentication use smart card for mangagers and basic authentication for others.