it works ok for me and i haven't changed a single thing: "Examples_V2.03MaxGranularGranular_Lemur_Main_Patch.mxb", GranularSynthesis.jzml template (2006-07-05), max/msp 5.1.7, os x 10.5.8, lemur os 2.0.3b6. i just load some samples and drag my finger around the center rectangle and i hear the granular audio. fun!
so it seems more likely the problem is a communication issue between max and your lemur. check your osc target settings. quit max, verify the jazz editor detects your lemur, load the template, make a [jazzserver] object with argument of the port number you are using, attach a [print] and check the max window while you press buttons (see pic). if all that works, try reverting to the granular patch before you edited it.