Ever since the upgrade to 3.0, I've had the following problem:
Plays one song. At the end of the song, it "encounters a problem" and makes me sign in again. After signing back in, it tries to play the same song that just ended. Then it gets stuck buffering.
Slacker BlackBerry is currently uninstalled. I sure am glad I didn't pay for it yet. Works fine on my PC or my SqueezeBox Boom.
check the slacker forums... It came up as a problem for others. Are you using a Leaked OS? these could be causing various issues that haven't popped up on the Officials.