Found this on the net. Can't say for sure it works.

To turn off AA for a single object or group:

1. Select the object or group.

2. Click the A button next to the object/group. The Object Attributes dialog will come up. 22 July 2008AZ 3D,

3. Press Ctrl+Shift+Alt and click on the OK icon in the Object Attributes dialog.

4. Render the scene. The object with the AA turned off will have rougher edges than other objects.

This is not my "second childhood". I'm not finished with the first one yet.

Time flies like an arrow; fruit flies like a banana.

"I'd like to die peacefully in my sleep like my grandfather....not screaming in terror like the passengers on his bus." - Jack Handy