I’ve update (apparently with no issue) the FEZ Hydra to 4.2.2.0 firmware, but display not working any more. MFDeploy can ping and VS deploy projects. I’m using Ethernet firmware and I used FEZHydraMainboardUpdater.exe included in 23-7-2012 release .
Anyone facing same problem ?
I respond to myself … Leaving Hydra alone for 1h during lunch, I found the display working … funny.
Maybe the Hydra was hungry and ate something while you were at lunch? 
From release notes “display is disabled by default”. All you need to do is make a gadgeteer project that includes the display and then it will work automatically.
Solved …
But really need 1h to enable !! … very amusing …
Yess I think so … I see the power supply little empty …