I am able to telnet from hyperic HQ instance to the RDS on the correct port, but not from Hyperic to RDS.

I'm not sure I understand this piece here. Did you mean to say

but not from RDS to Hyperic

I'm no AWS expert but a couple of things.

- ensure there's no internal db Hyperic HQ running as this won't allow you to connect to an external db

- is the proper db information configured in hq-server.conf?

- are the proper ports opened on the RDS spin up? The AWS permissions are a bit wonky at times.

If this seems basic, sorry, just trying to get more info over what you've tried.