Empty or null password retrieved for host
I'd need to see the whole log, but a lot of times this is caused by incomplete DNS resolution. I would make sure you got the correct A and PTR records for this host setup.
Search your log for "Caused by: java.net.UnknownHostException" - that indicates a DNS problem. If you still have problems try removing the host as mentioned.
Especially by uninstalling the agent manually (give your DB says it has an old agent)