I do get the same error. I tried changing the mode to "Session per User", still no luck.
I see following error in the log file as well:
2013-08-21 06:33:07.160+0000 WARN [AutoDeployManager] Unable to get AutoDeploy service! AutoDeploy host will be set INACTIVE! Reason: com.vmware.vim.vmomi.client.exception.SslException: com.vmware.vim.vmomi.core.exception.CertificateValidationException: Server certificate chain not verified
My setup has a vCenter appliance and the same appliance host the AD server.
I tried running few Powershell plugin workflows, which also returns "java.lang.nullpointer" error.
Regards,
Vaibhav