Form based security problem

[Guest]

I have developed a form based web authentication system: login.aspx

It has been working for one and half years. Since Yesterday it does not work
and there is no error message. All of my system have not been changed.

My computer is located in the intranet. Is it affected by security policy
set by coporate administrator?

Another case: I found the property of DIRECTORY SECURITY --> SEcure
Communication --> Server Certificate is not greyed. It was greyed out
before. Is it affected by this?

Thanks

David