problem - engine light - abs light - speedo at zero - allison 1st gear only

Today my 3 week old - 2800 miles Chevy Silverado 3500 Duramax Allison
4X4 dually had a BIG PROBLEM, while driving the following occurred.

the engine light, the abs light and the brake light went on - the
speedometer stayed at zero while moving - the allison trans stayed in
1st gear only - the display said "Service brakes" I had to drive on
the Penna turnpike at 15 miles per hour with the engine running at
2k...

If I stopped and turned it off, and then restarted it, it did not
shift into gear immediately...

I went to a chevy dealer - the tech said the diagnostic unit showed to
many error/problem codes... he spent 5 hours and didn't solve the
problem... he was in contact with the GM tech line people. they
thought it was a small part which they got from another dealer nearby.
That did not fix it. Now they think it is a control unit of some sort
on the allison trans. could not get one nearby - expect it to be
delivered from GM next week...

anyone have a problem like this???

I have a 1988 Buick LaSabre. two days ago my wife had pretty much the same problem. service engine soon light came on, no power, no speedo. I took it out later that night and it worked fine. I took it to work today and had the same problem she did. ( thats why Im looking in the forums now). If you find out anything PLEASE let me know.
TKS!

Update, I saw this. Hope it helps.
http://www.automotiveforums.com/vbulletin/showthread.php?threadid=105493&highlight=speedometer