Soundcloud devs made some changes in their code, and i don't know why, they are switching back to rtmp protocol.
Even the response said that track is streamable it can't be streamed with a regular stream_url.
After some digging in dev tools, i've noticed that some tracks use rtmp protocol instead of http/https
Anyway, you can find the streams of the track on:
http://api.soundcloud.com/tracks/TrackID/streams?consumer_key=XXX
from here, you're on your own. from my research, only flash (why?) can play rtmp streams.