Not sure if anyone else has come across this, but I have tried adding the @font-face attributes into the CSS Inserts section and it seems to cause an error in Atahualpa 3.4.9/WordPress 3.0 by reverting the settings back to default Atahualpa values. So it not only doesn't save @font-face, but it resets all the settings.
This error also occurs with Atahualpa 3.5.1/WordPress 3.0.
I have successfully gotten @font-face to work with Atahualpa 3.4.9/WordPress 2.9.2.
Is this a known issue with Atahualpa and WordPress 3.0?
For some reason it's not working on a newly created blog using Atahualpa 3.4.9/WordPress 2.9.2.
The site that is working OK - http://keeptechreal.com/
The site that doesn't work now - http://www.montessori101.com/