We've had the 04 H2 since May, and finally got a hold of a burned copy of a navigation disc (PN:22846887). Tried putting the disc in, and it said that it was updating. Got about 50% then it flashed a White screen with some writing that looked like Japanese, then it started the update over. After the third time, we tried ejecting the disc at the White screen.

After that we got a black screen with yellow Japanese, and right under that it said Se: Original CD-ROM. Tried putting the disc back in, but now all we get is a black screen. The backlight for the screen doesn't even look like it comes on anymore. Ejecting the disc, makes no difference.
The radio still plays, but none of the buttons work except seek and the volume ****.

Is there anyway to re-flash the radio? Can a dealer re-flash the firmware? Or is this unit totally screwed?

 

I don't know how much you googled, but I couldn't find much on the topic.
I'd want to see how much a dealer would even want to do a diagnostic scan on it & how much a flash would be. There'll be a point where the money you throw into it can go towards a much better nav unit.

 

If you still got the iso image of the DVD, try burning it at the slowest speed (2.4x or lower if possible)
And, depending on your burning app, set BOOK TYPE to ROM

I had similar problem with "cant read from dvd" errors popping up like every 10-15 minutes. I reburned at a slower speed and problem went away

 

Update: Got the Nav unit back up and going. Just before heading out to spend $500 at Best Buy, I thought i would try disconnecting the battery (should have been the first thing i did). Disconnected the battery and let it sit for 15-20mins. Then let the key sit at the "on" position for a few minutes to let the actuators calibrate. After a few minutes the head unit came back on.
It will not read the map disc, but oh well the screen is back.

 

Good news!
You could try what atari said to do. He's correct about that & I can verify.

 

MidTNHummer, after you reconnect the battery, what does letting the "actuators calibrate" actually do? Got a similar issue going on, the display for the radio stopped working, but I have full functionality with the steering wheel controls. Trying to troubleshoot this thing before I have to go back to the "Stealership" for help. This may be the sign I need to just buy new head unit...

 

The actuators I was referring to are the HVAC actuators. I'm paranoid about those things. Have replaced all four this year.

I left the disc in the unit then disconnected the negative terminal on the battery. I put the key in the "on" position just to drain everything. Let it sit 15-20 mins, reconnected and left the key in the "on" position for about 5 minutes before trying to start it.

 

mid good thing you solved the problem . i have a 04 also without the factory nav . a good friend in texas also had a 04 with the same problem and after talking over the phone with a service guy from what used to be a hummer dealer he also told my friend that unpluging the batt should solve the problem he also looked up the vin on his end and find out that the H2 did not come with a nav unit so we are guesing the previews owner had the 6 cd changer and had this nav install from another truck on its own ...