Add me to this list of dissatisfied customers. I bought my first non-ipod and now I regret it. First I had some inane terms of service issue(it wanted me to agree but gave me no opportunity to agree)then once i finally got that fixed it let me sign in from the zune software one time, I chose some stuff to download for my free 2 week zune pass trial and went to bed with my zune syncing and the stuff downloading. I woke up and only the music already on my computer had synced to my zune, the stuff i lined up to download from the marketplace through the zune software just never downloaded. tried opening and closing the zune software and when i tried to sign in i just get that same error message with the original id 80048051.
Since then I have done everything on that help page and still nothing. I can sign in zune.net fine from a browser and I can access the internet through the zune software( i know this because i can browse the marketplace sucessfully through the zune software i just can't sign in to buy anything) so it's pretty surely NOT a firewall issue... i dont really see how it could be an issue which stems from my computer since i am able to browse the marketplace just not sign in.
I'm just astounded that this is the experience microsoft rewards us with for choosing them over the ipod. I should've known better. I like how my zune looks, and it seems to work equally well as my old ipod... but so far it's just a huge hassle to do even basic things with it.