I am getting the error.
SERVER UNABLE TO PROCESS REQUEST. FAILED TO PUBLISH WORKFLOW. ERROR WHILE UNLOADING APPDOMAIN.
We get it sometimes, and sometimes not, so probably there ia problem in one of the loaded balanced server of sharepoint.
some body suggested me
"Seems to be an issue with access for COM component. Run it with Server admin user or farm administrator". I dont know what is COM component though.