Nvidia and AA

[Feuerfalke]

Are you running a fresh installation or did you upgrade your drivers at any point?

If you didn't clean your registry from remains of previous driver-settings, it's possible that you will not be able to actually save your changes (even though it may look like it).

I recommend nHancer. You can download this tool for free and once installed you can override any setting, no matter if there is a conflict with older driver-settings or not. You can also fine-tune some options with quick access.