Which NIT are you using? What verison of the O/S do you have?

On my N800 with diablo (4.2008.36-5), I was able to get deezer.com to work, but it was very slow. It took about 2 minutes for the player to start working. I couldn't get musicme to work since it said that my version of flash was too old.

You might also try pandora.com and slacker.com. They both provide free music and work on my N800, albeit a little slowly.