I am another with this problem. I can have just one audio clip in a project and it crashes every time and after a long (time and distance) phone call to Cakewalk support last week and a couple of email exchanges since, I still have the problem.
Here were the suggestions by Cakewalk;
Enable cronus.dll - done
Use a mono clip - done
Use a short clip - done ( I assume 1 measure is short enough)
Make sure the track is not still armed - done
I have just unregistered and register cronus.dll as per the suggestion above too and then re-enabled it.
It makes no difference with an imported audio clip or one recorded directly in to Sonar.
I am awaiting my next response from Cakewalk but they only come back after a couple of days.
So if anyone has any other ideas, they would be appreciated.
Cheers.
FYI: Win XP Sp3, C2D 2.26, 4Gb ram, onboard IDT audio, asio4all v2.9.