I have had the same problem every time I've installed PMS on OpenSUSE, and I always forget how to fix it. The problem is that PMS requires Java 6 (see here: http://wiki.qnap.com/wiki/PS3_Media_Server
You probably already have Java 6 installed--I did. Just check somewhere like /usr/lib64/jvm for different installations. For me, running the command "export JAVA_HOME=/usr/lib64/jvm/java-1.6.0-openjdk-1.6.0/jre/" before running PMS.sh did the trick. You can add this line (or whatever you need to point JAVA_HOME to the right location) to your .profile in order to get the right Java path every time you open the console.