I was able to fix this problem this morning.

Firstly, I opened all the ports required for the Playstation Network as described in the guide for my router at portforward.com
http://www.portforward.com/english/routers/port_forwarding/routerindex.htm

Then it still failed.

But when I went on the PS3 XMB screen and went to Network Settings and turned OFF Connection to Media Servers...

POOF! It worked right away.

I re-downloaded Warhawk to no avail. So I'm still stuck unable to upgrade to 1.20.

DMZ'd the PS3, went to manual DNS & IP settings... all nada.

Everything else works great, network-wise, just not the Warhawk 1.20 update download. :(

Go to game data and delete warhawk, then install it again. It worked for me.KittensWithBeer

Was the re-downloaded full version of the game already patched, or did you still have to do the first run-quit-download patch ?

I too have recently purchased the d/l version of Warhawk on the PS Store and downloaded it without a hitch.

On the first launch, it does its version check and prompts me to quit & download the 1.20 update.

And the 10 times I've tried this over the last three days have all failed with an error:

An error occurred during the download operation.
(80710723)

I've read a number of the posts around the 'net that reference this same error code last january and suggest a fix of adjusting to manual DNS/IP assignment for the PS3 and/or DMX'ing the box.

A better explanation that I found on the official board suggests that the download servers are overwhelmed for the patch and that there's a higher likelyhood of success during off-peak hours.

ref:
http://boardsus.playstation.com/playstation/board/message?board.id=warhawk&message.id=207252