Felt a bit silly even just asking this here.
I'm getting exactly the same problem with one of my SA4000's and ACE, but haven't had a problem before. What version of the IVE O/S are you on? I'm on 6.3R3.
There is a port blocked between IVE internal IP and RSA Server IP.
I think it was UDP5500 or something like that. Read the Documentation.
Pinging RSA Server is not enough. Check Firewall between the two devices.