I can't write automation all of a sudden on any track.  Is there a global setting that turns it off?
I've tried Clearing all automation write enables and re-enabling parameters, but it does not record my automation when I move the mouse.  I tried restarting Sonar.
 
I'm using X2 Studio build 306.
 
Thanks.

I cannot tell by the build number if that is X2a. There were a substantial number of automation fixes introduced in X2a. http://www.cakewalk.com/S...reader.aspx/2007013301

With X1 Expanded I have had this happen a few times. I believe it was corrupt project files, as in every case I had to export the audio, then recreate the song from scratch and import the audio. Major pita when it happens.
 
If you haven't done the X2a update, then yes - you should do it! Hopefully that will resolve the problem for you.
 
EDIT: Sorry, I just noticed your problem is "write automation". My problem may have been the same, but it also was not reading any automation either.

Check whether you've got auto-punch enabled.  If so, you can only record in-between the punch points.

ston
Check whether you've got auto-punch enabled.  If so, you can only record in-between the punch points.

This was the issue, thanks.