Pavel,
What version of the Object Adapters are you using?
If you enable verbose workers in the Worker Agent Administration (under Site > Utilities), restart the Doc worker and republish do you get any further output in the worker_#.log generated on the CAD worker?
I am assuming that you're doc worker utilizes the Adobe LiveCycle Server. The version used there along with the jboss log could also be helpful here.
Thanks,
Lori