The error "unable to download manifest" is because the servers are down. Closed Beta ended last night at midnight, and this date was communicated WELL in advance of the shutdown. The workaround is to wait until the servers are no longer down. The fix is for Adhesive to launch Open Beta, which is scheduled to begin on 12/12.
If you used the search function, you might find that threads like this have been created
every single time a closed beta event ended, and the answer has always been the same: The servers are down. You cannot play the game. The error messages you are receiving are because the servers are down. You need to wait until the next beta event begins.
We're out of the loop because we aren't on Adhesive's internal development network with test servers and the unstable client builds.
I mean, if you want to see your garage, you should be able to launch the game directly by navigating into your Hawken folder and going into BinariesWin32 and launching HawkenGame-Win32-Shipping.exe but it STILL won't be able to connect to any servers because, you know, they're down.
It's a shame that you didn't get much time to play before the beta event ended, but the good news is that Open Beta is about to start, and it'll be full-time (barring maintenance downtime, obviously).
Edit: If you search for "unable to download manifest" in the beta subforums, you'll get a lot of results that aren't post-beta questions like the one I described above. Many threads were when the test period was active, and in these cases, the servers were... still down, but this was due to technical issues instead of a planned shutdown of the game. And again, the only solution was to wait for Adhesive to get it fixed.
Edited by Elix, December 07 2012 - 06:11 PM.