I was having the same problem with it hanging when attempting to play it. I was getting a 503 error to to a java.lang.OutOfMemory.Error. I changed my jetty.sh file to include a line to increase java heap size like this:

JAVA_OPTIONS="-Xms16m -Xmx128m"

I am using JReceiver 0.1.9. Currently it only works for one Rio at a time, and I still get intermittent 503 errors. I also haven't really figured out the optimal amounts of memory to allocate. Finally, the application seems to be quite CPU intensive (I'm running it on a Celeron 1.1GHz and I go from ~15% to ~75% usage).