I signed up for xbox live and it won't progress to the gamer profile using those credentials on live.xbox.com. I say I'm a member of xbox live, say I have a 360 and then I get this: That's using the email and password I used to sign up to xbox live on the 360. I then choose the bottom choice and it takes me full circle to the first question again.
I think you have to link your xbox live account with a .net passport thingy, but I would've thought that the signup process you described (I wouldn't know the process as I havn't signed up to a 360 live account before, I just converted my old one) should make a passport or something : / Try signing into xbox.com with a .net passport, like the one you use for msn or something, and then see if you can link your live account with your passport. It could also be you have to wait a while for it to go through, so if you tried logging in the day you made the account wait 24 hours to see. If none of this works give MS a ring or send them a e-mail.
I linked a 360 (silver) account to my dad's hotmail account, so he could log in and download stuff if he wanted - it was just a matter of typing in his email addy and password. Didn't seem to have any problems doing it this way and he had his one month of XBL gold (even if he didn't end up using it).