Hello,
I have read your comments very interested, because I have exact the same problem. I have tried all the steps you have described, but the problem is still there.
We have two LiveUpdate-Administrators and 4 SEP Managers. When I configure the liveupdate policy for the clients to connect directly to the LiveUpdate-Server then all signatures were updated. When I configure the policy to automatically download the update from the SEP Manager the updates were not assinged and in the LiveUpdate "Donwload Status" in the SEP Manager old virus signatures are shown.
I think it is not a problem of LUA ?!
Next step for me is to open a incident for this problem