Yes I found out my problem. I used to live in Canada. I purchased a Zune 120 while I was there, and setup my DechahZ account with my Canadian address. I now live in Australia (since last July). In Australia I had my Win 7 based computer set to Australia in the Regional Settings. With Zune 3 software this logged in without problems, but with Zune 4 software this is a no no. I finally changed the regional settings back to Canada and finally I can get back into my account from the Zune player software. Though I notice that I have now lost the Marketplace menu option in the Zune player software. Oh well, I never could buy anything from it anyway, but I did like checking out the Channels occasionally to find new music.
I have no idea why Microsoft needs to be so anal about who can see aspects of the Zune service. Apple still lets people look at their various online stores around the world, even if you are barred from buying anything from those stroes due to geographical restrictions. With Zune, unless you have a profile based in the US, then you cannot see the Marketplace at all.