Notice the difference between the old and new login page:
- CRM4 + IFD login page
-> you can start straight away with typing your username
-> you only need to enter your username
- CRM2011 + ADFS
-> you need to click on the username first
-> you need to enter 'domainname\username'
Modify these routines in FormsSignIn.aspx.cs (change domainname to your domain), located in C:\inetpub\adfs\ls (make a copy of the file first):