I just got a new 5510 and need to get a polycom head unit to NAT through and it doesn't want to seem to play nice. (At least that is what I think it is) I have set up a static nat for the unit itself and set up an outbound and an inbound ACL to that unit of allowing all IP traffic (just to test). I have tried not inspecting the H323, inspecting the H323. Telling the unit that the firewall is H323 capable and not and it still doesnt' work.
I can hook the unit behind a 515e and mimic the same settings and it works fine. I packet trace from within the ASDM of the ASA unit and it fails on the NAT portion of the test.
Sorry to be so vague. I am at a bit of a loss.