I am having a similar problem. I had a perfectly good 4.1.2 server running.
I downloaded the 5.0 iso, created the CD, booted the server from
the CD, and chose upgrade. After about 10 minutes of doing its
thing it said it completed correctly. I restarted and logged in
as admin. I tested the Internet connection and all was well. I
then went to one of my Windows boxes and booted it. I couldn't
get to the Web. It wasn't even getting an IP from the server.
WINIPCFG showed 169.x.x.x address. Did a relase all/renew all
and got nothing. Tried two other of my Windows machines. Same.
Rebooted server. Same. Intalled the update 1 blade. Same.
I am writing this from withing the text browser from the admin
console.
Any thoughts? I checked all the settings and all appears to be
the same as under 4.1.2 but it doesn't work now.