ASP.NET SSO not working despite of matchin machineKey and authentication settings

I have a single website that can be reached on our development system and my local machine. By modifying my hosts file I'm trying to make SSO to work. It simply doesn't, despite the two sites are being practically identical.

The odd thing is that SSO only doesn't work when the other copy of the website is hosted on that particular development machine. If I set it up on an other machine and my local machine, SSO works flawlessly.

The only difference between the development system and my machine is the operating system and the fact, that the website is precompiled on the development machine.

It's also interesting that SSO works when every site is hosted on the development system.

Is there anything on a machine or web site that influences the encryption and decryption of forms authentication cookies other than the machineKey section of web.config?

It's worth noting that the length of cookie values generated by 开发者_StackOverflow社区the development system and mine are different. Cookies generated on my machine are almost twice as long usually.

Make sure to even out the "forms" node by all attributes, i.e. entries in both application web.configs should have identical "forms" nodes

That particular machine (or all other machines) have installed the MS10-070 update, also known as the fix for "ASP.NET Padding Oracle Vulnerability" (CVE-2010-3332).

Run Windows Update on everything and it should sort itself out.