online update doesn't work

I'm trying to update online to 9.0.2 and always I'm told that the update server doesn't respond:

I don't understand how this could be a firewall problem unless Adobe wants to connect actively

from the outside to a port of my computer (which is indeed connected through a firewall and a NAT gateway).

I don't have problems doing other Adobe upgrades (like Flash or Adobe Reader) this way.

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Christoph